Level 14: Arcturiadoom

Arcturiadoom is designed for four 13th-level characters, and adventurers who defeat the monsters on this level should gain enough XP to advance halfway to 14th level. The lich Arcturia, who dwells on level 23 of Undermountain, is one of Halaster’s most accomplished apprentices, arguably the most powerful of the Seven, and a master of transmutation magic. Arcturiadoom is her personal retreat (“doom” being an archaic term for a lord’s domain). Hidden on this level is Arcturia’s phylactery, and adventurers would be wise to find and destroy it before facing the lich in battle on level 23.

What Dwells Here?

Arcturiadoom has been taken over by fire giants in the service of Halaster. The fire giants are accompanied by a large force of hobgoblins. Drow have also infiltrated this level of the dungeon, though they have no quarrel with adventurers.

Fire Giants

Emberosa, a fire giant, has come to Undermountain with six of her kin on a mission to raise fire giants to the top of the giant ordning, dethroning the mighty storm giants.

Emberosa hopes to obtain a lost rune of power created by the giants more than forty thousand years ago. She believes dwarves stole the rune from the giants and hid it under Mount Waterdeep. Halaster found the rune and hid it in on level 23, but he has agreed to part with it if the fire giants use their exceptional metal-forging abilities to build a giant construct for him. Work is under way, with the construct being assembled in area area 15.

For more information on the giant ordning, see the “Giants” entry in the Monster Manual.

Death’s Head Phalanx

The Death’s Head Phalanx is a force of hobgoblins that came to Undermountain along with Emberosa and her fire giants. This force is commanded by a hobgoblin warlord named Doomcrown, who is the estranged son of Warlord Azrok (see level 3).

A devout follower of the godslayer Maglubiyet, Doomcrown wants fire giants to ascend to the top of the giant ordning, envisioning their brutal tyranny sweeping across Faerûn. He expects to play an important role in Emberosa’s ascension and conquest, and he dreams of ruling what remains of the High Forest once the elves and other forest denizens are purged and the trees are reduced to ashen spines.

Since arriving in Arcturiadoom, however, Doomcrown has developed strange habits. He spends more and more time locked away in his quarters, chasing some strange new obsession. His followers remain loyal, but they worry about the mental state of their warlord.

Hobgoblin Patrols

Hobgoblins of Doomcrown’s phalanx have secured most of the halls and chambers in Arcturiadoom. Consequently, the only wandering monsters of consequence are hobgoblin patrols. A typical patrol consists of four Hobgoblin. Their marching footsteps and clanking armor can be heard well in advance of their arrival, and characters can’t be surprised by them. Combat with a patrol is sure to alert other creatures in the vicinity.

If any hobgoblins are defeated while on patrol, subtract their numbers from the guards in area area 32a.

House Freth

Three drow mages have infiltrated Arcturiadoom in the hope of securing powerful magic to conquer other levels of Undermountain. These drow belong to House Freth (see level 12). They avoid violent confrontations with adventurers and instead try to turn them against the fire giants and the hobgoblins.

Polymorph Traps

Throughout Arcturiadoom lie magic traps designed to polymorph humanoids. (Creatures that aren’t humanoids are unaffected.) These traps are marked P on map 14. The hobgoblins are aware of these traps and do their best to avoid them. A polymorph trap is marked by a nearly invisible glyph inscribed on a 10-foot-square section of floor. A character searching the area for traps can detect the glyph with a successful DC 20 Wisdom (Perception) check. The first humanoid to pass over the 10-foot-square area triggers the glyph and must succeed on a DC 20 Wisdom saving throw or be transformed into a monster with average hit points. All items worn or carried by the creature are absorbed into its new form. The new form is hostile toward all other creatures and must attack any other creatures it can see. Roll a d10 to determine the creature’s new form:

| - | - | | 1. Carrion crawler | 6. Hook horror | | 2. Chimera | 7. Manticore | | 3. Fire elemental | 8. Otyugh | | 4. Gelatinous cube | 9. Owlbear | | 5. Gorgon | 10. Wyvern |

When the polymorphed creature drops to 0 hit points, it reverts to its original form and is stable at 0 hit points. Once a glyph is triggered, it disappears, rendering its space safe to pass through until Arcturia sees fit to replace it. A successful dispel magic spell (DC 17) cast on a glyph removes it.

Exploring This Level

All location descriptions for this level are keyed to map 14.

1. Entrance to Arcturiadoom

These caverns lie at the end of the worm-bored tunnel leading down from level 13.

1a. Worm Tunnel

The bore worm on level 13 wanders down here occasionally, looping around a central column of rock before traveling back up. This column supports the cavern’s 30-foot-high roof. The cavern also has these features:

Double Door. A double door is framed with carvings of worm-ridden skulls. Carved into the lintel above the double door is a sconce sculpted to resemble a skeletal hand, with a continual flame spell cast in its palm.

Monsters. A pair of stalagmites flank the double door. Hiding behind each stalagmite is an invisible drow mage and an invisible quasit.

Rock Formations. Around the edges of the cavern are more stalagmites and stalactites. More of these formations fill a smaller cavern to the southeast (area area 1b).

The two drow mages are males named Hulziin and Yrrprek. Each wears a cloak pin bearing the insignia of House Freth. They arrived here shortly before the adventurers and have greater invisibility spells cast on them. The drow and their two quasit companions try to remain hidden, allowing adventurers to move into Arcturiadoom ahead of them. Once the path is clear, they pass through area areas 3 and area 35 on their way to area area 38.

One of their kin, Vanar, arrived early to scout and has already slipped inside. The characters might encounter him and his shadow demon in area area 29.

1b. Stalactites and Stalagmites

This damp, dripping cave contains a veritable forest of stalagmites and stalactites.

1c. Claw-Shaped Cave

The drow have hidden supplies in the deepest arm of this otherwise empty cave. A search reveals three backpacks made of woven spiderwebs. Each pack contains a mess kit, 10 days of rations (dried mushrooms, moss, and boiled cockatrice eggs), 50 feet of spider silk rope, and a full water skin made from a lizard’s bladder.

2. Natural Caves

This small network of caves lies outside the dungeon proper and serves as home to one of Arcturia’s monstrous experiments.

2a. Deformed Duergar

Characters who enter this cave are soon attacked by a hideously deformed duergar. The creature has enlarged itself to a height of 9 feet.

This creature used to be two separate duergar, a male named Blork and a female named Muatha. Arcturia fused them together into a single creature by using magic that only a wish spell can undo. Both skulls merged into one bulbous head that has three ears, three eyes, two noses, and two mouths. It has a third arm on the right side of its body, and its left leg splits into two at the knee, giving it three feet. The transformation drove the poor creature insane, and it regards all other creatures as threats that must be destroyed.

The creature is a duergar, with these changes:

• The creature has 40 hit points.
• It has advantage on Wisdom (Perception) checks and on saving throws against being charmed, frightened, stunned, or knocked unconscious.
• As a bonus action, it can make an attack with its javelin.

2b. Duergar’s Crib

The deformed creature in area area 2a sleeps here on a bed of spongy black mold that grows at the back of the cave.

2c. Fungus Gardens

The creature in area area 2a comes here to feed, as do other creatures dwelling in the caverns. The cave has the following features:

Fungi. Gardens of fungus sprout from mounds of offal on the uneven floor. The fungi release clouds of dimly luminescent spores that fill the cave like a fine, hanging mist.

Carrion Crawlers. Four Carrion Crawler dwell here. Two cling to the 10-foot-high ceiling, and two feed on the rotting corpse of a fifth carrion crawler lying amid the fungus.

The crawlers are natural enemies of the creature in area area 2a, which recently killed one of them with a blow from its war pick. They ignore characters who keep a respectful distance.

A character who studies the fungus and succeeds on a DC 10 Intelligence (Nature) check can distinguish edible varieties from poisonous ones, and also ascertains that the spore clouds are harmless. A character unaware of this information who eats fungus has a 50 percent chance of consuming a poisonous variety and must succeed on a DC 10 Constitution saving throw or be poisoned for 1d4 hours.

2d. Standing Gate to Level 12

This cave contains a pair of standing stones with an inanimate minotaur skeleton embedded in each one, facing each other. These standing stones form one of Halaster’s magic gates (see “area Gates"). The rules of the gate are as follows:

• Any creature that touches one of the standing stones is targeted by a maze spell (save DC 22).
• To open the gate, a creature must escape the labyrinth created by the maze spell. When it returns, the gate opens for 1 minute.
• Characters must be 12th level or higher to pass through this gate (see “area Jhesiyra Kestellharp"). The first creature to pass through the gate triggers an elder rune (see “area Elder Runes").
• A creature that passes through the gate appears in area area 12a on level 12, in the closest unoccupied space next to the identical gate located there.

3. Foyer

Monsters. Two male Fire Giant (named Druvax and Zelzzarf) and seven Hobgoblin are sorting through pieces of scrap iron on the floor and tossing them noisily into piles.

Statues. Two statues of dwarves flank the double door to the southwest. Each statue stands atop a crumbling, 2-foot-high stone block. The statues have been magically reshaped in gruesome ways.

Arcturia used stone shape spells to mutilate the statues, which once depicted proud dwarf warriors. The statue to the west has stony pseudopods sprouting from it, while the statue to the south appears half-melted.

The giants and the hobgoblins aren’t happy with drudge work and eagerly hurl themselves into combat if the chance presents itself. The scrap iron was brought down from level 13 and will later be transported to area area 14 to be eventually melted down and recast.

4. Prison

Arcturia confines living subjects here until she finds time to experiment on them. The 15-foot-high room is engulfed in a permanent antimagic field (see the antimagic field spell for effects). The room has the following additional features:

Cells. Six 10-foot-high cells with arched ceilings are barred with iron portcullises. Lying in the southwest cell is a humanoid corpse clad in plate armor and riddled with arrows.

Lever. Bolted to the floor in the middle of the room is a 4-foot-wide, 7-foot-long iron plate with a comb-shaped hole in it. An iron lever protrudes from the hole.

The remains in the southwest cell are those of a female orog who was captured by Arcturia and stripped of her weapons. The hobgoblins found her, shot her full of arrows through the bars, and left her corpse to rot.

The iron lever operates the mechanism that raises and lowers the portcullises by sliding it along the comb-shaped hole in the floor plate. Depending on how the lever is positioned, it can be used to raise any of the portcullises one at a time, or to lower all the portcullises into place.

The portcullises are impervious to weapon damage. The gaps between the bars are 4 inches wide. Closed portcullises are locked in place; forcing one upward requires a successful DC 26 Strength (Athletics) check.

5. Side Chambers

Other than a polymorph trap (see “area Polymorph Traps"), these conjoined rooms contain little of note.

5a. Domed Chamber

This room has a domed ceiling 20 feet high. It is otherwise empty.

5b. Teleport Destination

This chamber has a flat ceiling 15 feet high. Creatures teleported from area area 13a arrive here. The room is otherwise empty.

6. Statue of Arcturia

Here marks the perpendicular intersection of two corridors, one cut short by dead ends. Beyond an archway to the southwest is a stone statue of a 6-foot-tall skeletal figure with butterfly wings sprouting from its back and sharp bone spurs on its forearms and elbows. The statue stands atop a 3-foot-high stone base. The statue clutches a stone wand and points it toward the floor.

The statue represents Arcturia and is neither magical nor animate. The statue’s wand points in the direction of the polymorph trap that is set before it (see “area Polymorph Traps"). Characters who search the floor for traps have advantage on checks made to detect the polymorph trap.

7. Statue of Halaster

Set into an alcove at the back of this dusty side chamber is a nonmagical, life-size statue of Halaster Blackcloak carved from granite. The statue is thrusting its stone staff outward in a threatening manner, its visage sculpted with a look of wild abandon. Its robe is engraved with hundreds of lidless eyes. The statue stands atop a 1-foot-thick granite disk.

Mithral Keys

A character who inspects the statue and succeeds on a DC 15 Wisdom (Perception) check discovers that one of the eyes carved into Halaster’s robe is a button. Pressing this button causes two keys tucked under Halaster’s robes to clatter onto the floor around the statue’s base. Each key is a flat, 6-inch-long piece of mithral worked into a curious shape.

The first key is shaped like an F, the second like a V with a small loop at the bottom. These are two of the six keys required to activate the weapon of mass disintegration in area area 37.

8. Dwarven Crypt

This room is a dusty crypt with an arched ceiling 20 feet high. It has the following features:

Sarcophagi. Four limestone sarcophagi with faded Dwarvish inscriptions line the room’s perimeter. They contain only dust, shards of bone, and strips of moldy cloth.

Polymorph Trap. One 10-foot section of floor bears a hidden polymorph trap (see “area Polymorph Traps").

9. Death’s Head Watch Post

The hobgoblins of the Death’s Head Phalanx have set up an outpost here to guard the foundry (area area 12). Characters approaching this part of the dungeon hear the war chants of the hobgoblin phalanx in area area 9c.

9a. Training Room

Characters who listen at the door hear guttural cheers coming from within. The room contains six Hobgoblin. Two are engaged in mock swordplay with dulled blades in the middle of the room while the other four cheer them on. The room is otherwise empty.

9b. Crypt

A granite sarcophagus against the north wall has been opened, its lid dumped onto the floor. Dust and cobwebs cling to its sides, obscuring ancient inscriptions.

The sarcophagus contains the dusty remains of a Melairkyn dwarf entombed here thousands of years ago. The inscriptions on the sarcophagus, written in Dwarvish, translate as follows: “Thou hast found the final resting place of Harlsnod Darkshine—architect, trap builder, and drinker of fine ales.”

9c. Hobgoblin Phalanx

Here, a hobgoblin captain has marshaled a phalanx of twenty Hobgoblin. The captain faces east and recites a liturgy in Goblin to the dread god Maglubiyet while the soldiers stand at attention in two rows of ten, facing west. As she reaches dramatic peaks in the liturgy, the hobgoblins grunt and nod approvingly, banging their fists on their armor.

The hobgoblins attack intruders on sight. A battle here pulls reinforcements from area areas 9a, area 16, and area 18. It also attracts the attention of the fire giant metalsmith in area area 11.

10. Dwarves' Den

Tankard. A large iron tankard sculpture has torn loose from the 30-foot-high ceiling and fallen onto a stone table in the middle of the room, cracking it in half. Toppled stools surround the broken table.

Statues. Two 4-foot-tall statues of dwarves stand atop 2-foot-high blocks of stone at opposite ends of the room. The head of the southern statue has broken off and lies on the floor nearby.

This cast-iron tankard once hung from the ceiling by iron chains and is big enough for four dwarves to crawl inside. It weighs 1,500 pounds and makes a satisfying, bell-like clanging sound when struck—and the noise draws hobgoblins from area 9c.

Statues and Mithral Key

The north statue depicts a smiling female dwarf raising a stone tankard. Hidden in the tankard is a flat, 6-inch-long mithral key shaped like an H missing its top left stem. This key is one of six required to activate the weapon of mass disintegration in area area 37.

The south statue depicts a headless male dwarf resting a large pair of stone tongs on one shoulder; its head cracked when it hit the floor, and it falls apart into two halves if disturbed.

11. Smithy

Characters who listen at the doors to this room hear loud hammering from beyond. The 30-foot-high room is warm and contains the following features:

Fire Giant. In the middle of the room, a male fire giant uses a massive hammer and anvil to pound a heated iron fragment into a rounded shape.

Fire Beetles. Resting on the floor next to the oversized anvil is an iron cage containing fifteen brightly glowing Giant Fire Beetle. (The giant uses the cage as a lantern.)

Iron Pieces. Wings to the west and east contain pieces of sculpted iron of all shapes and sizes.

The giant, Hrossk, is hostile toward adventurers. He keeps his greatsword close at hand and hurls large metal cogs instead of rocks. Combat in this room can be heard by the fire giants in area area 12, who investigate at once if a fight breaks out.

Hrossk’s job is to recast hot iron into body parts for the giant construct in area area 15. Without Hrossk, Emberosa lacks the metalsmithing skills needed to finish work on Mecha-Halaster. Hrossk is currently crafting a piece of what will become one of the construct’s eyes.

The fire beetles can’t harm anyone while confined to their cage. Unlatching the cage door requires an action. If released, the beetles attack indiscriminately.

The iron fragments littering the floor include curved sheets of outer plating, as well as internal gears, cogs, spindles, bars, and pipes. These pieces are waiting to be attached to the construct in area area 15.

12. Melairkyn Foundry

The foundry is unbearably hot. Characters who linger here for 1 hour or more while the forges are operating are subject to the effects of extreme heat (see chapter 5 of the Dungeon Master’s Guide).

12a. Hell Hounds

Ceiling. This hall has an arched, 30-foot-high ceiling.

Hounds. Five Hell Hound patrol the hall. They obey the commands of fire giants and attack intruders on sight.

Open Pits. Three 10-foot-square pits in the floor contain discarded scraps of metal.

The pits are 70 feet deep but partially filled with scrap metal that reduces their effective depth. The western pit is 20 feet deep, the central pit is 50 feet deep, and the eastern pit is 10 feet deep. Any creature that falls into the pit lands on jagged shards of metal and takes slashing damage instead of bludgeoning damage from the fall.

12b–12d. Elemental Forges

These three identical chambers have stone stairs that climb 10 feet to each platform, at the back of which is a raging hot forge of blackened stone. The curved ceilings in these chambers are 20 feet high.

Three Fire Giant (two females named Dralkana and Ingritt and a male named Yarshoss) are stationed here, one at each forge. Their job is to melt down fragments of scrap iron so that Hrossk, the fire giant metalsmith in area area 11, can reshape them for the construct in area area 15. It’s tedious work, and the fire giants are restless and spoiling for a fight.

The fires in the forges are conjured from the Elemental Plane of Fire. A stone lever built into each forge closes a valve in the back of it, extinguishing the flames. Any creature that enters a lit forge or starts its turn in one takes 55 (10d10) fire damage.

13. Transmutorium

Arcturia keeps some of her horrific handiwork here.

13a. Woven Eyes

Pillars. Three pillars of polished black stone stand in the corners of the room. Attached to each pillar at waist height is a tarnished silver knob.

Tapestry. A huge, sickly purple tapestry hanging on the west wall undulates as though alive. Its surface is covered with eleven unblinking eyes: one large central eye and ten small peripheral eyes. (Hidden behind the tapestry is a secret door.)

Crystal Door. A crystal door in one corner of the room stands closed. Beyond the door is a small, magically lit chamber. (See area area 13b for details.)

All three pillars and their silver knobs radiate auras of transmutation magic under the scrutiny of a detect magic spell. Any creature that touches a pillar’s silver knob is teleported to area area 5b. Once a silver knob has teleported a creature, it disappears. Eight hours after the last knob vanishes, all three reappear.

Tapestry of Eyes

The fleshy tapestry is Xebekal, a beholder that invaded Arcturia’s dungeon years ago. The lich snared the eye tyrant and used a wish spell to transform it. In the form of a tapestry, the beholder retains its darkvision and can see whatever is in front of it, but nothing behind it. It can’t speak, and its movement is limited to harmless flapping. It can’t use its Antimagic Cone trait or take any actions or reactions.

Xebekal can be contacted with telepathy. It promises wealth and power to anyone who restores it, but has no intention of honoring its promises. Only a wish spell can turn the tapestry back into the beholder it once was.

The tapestry has AC 5, 33 hit points, immunity to poison damage, and vulnerability to fire damage. If it is reduced to 0 hit points, the tapestry is destroyed. The characters gain no XP for killing the beholder in this form, given its present helplessness.

13b. Alteration Chamber

Crystal Door. The door to this chamber is made of 3-inch-thick transparent crystal.

Brass Panels. Embedded in the wall next to the door is a brass panel with four brass buttons arranged in a diamond formation. (A similar panel appears inside the chamber.)

Light. A crystal dome in the ceiling sheds pale white light, illuminating the whole chamber.

Key. Lying on the chamber floor is a flat mithral key.

The buttons on each brass panel and their effects are as follows:

The top button is engraved with an arrow pointing up. Pressing it opens the crystal door, which retracts into the ceiling. This button is locked and cannot be pressed if the door is already up.

The bottom button is engraved with an arrow pointing down. Pressing it shuts the crystal door by lowering it back into place. This button is locked and cannot be pressed if the door is already down.

The left button is engraved with a tiny human stick figure. The button is locked and cannot be pressed while the crystal door is open. If the button is pressed while the door is closed, the light emanating from the crystal dome on the ceiling flickers, and all creatures in the chamber behind the door magically shrink as though affected by the reduce effect of the enlarge/reduce spell (no saving throw allowed). The effect lasts for 24 hours.

The right button is engraved with a larger human stick figure and functions like the left button, except the creatures in the alteration chamber are enlarged instead of reduced.

If a magically reduced creature is subjected to the chamber’s enlarge effect, or a magically enlarged creature is subjected to the reduce effect, the two alterations cancel each other out, and the creature reverts to normal size. The effects of the chamber aren’t cumulative—a reduced creature that is reduced again or an enlarged creature that is enlarged again doesn’t change size further.

Each time the alteration chamber’s reduce effect or enlarge effect is activated, roll a d6. On a 1, the chamber malfunctions. Instead of the normal effect, all creatures inside the chamber must make a DC 20 Constitution saving throw, taking 44 (8d10) force damage on a failed save, or half as much damage on a successful one. You can replace this damaging effect with a more benign one. For example, the chamber’s magic might cause creatures' noses to elongate or turn their skin blue; an alteration of this sort can be undone with a greater restoration spell or similar magic.

Mithral Key

The flat, 6-inch-long mithral key is shaped like a J with a loop at the top. This key is one of six needed to activate the weapon of mass disintegration in area 37.

14. More Scrap Iron

Light. Mounted to the diagonal walls at this intersection are four iron torch brackets with continual flame spells cast on them.

Scrap Iron. Heaped in the middle of the intersection is a 9-foot-high pile of scrap iron.

Double Door. A 20-foot-tall double door blocks the hallway to the north. Leering skulls are carved around the door.

The scrap metal came from level 13. Whenever the characters leave this area and return, there is a 20 percent chance that Hrossk, the fire giant metalsmith in area area 11, is here to collect a choice piece of scrap iron and bring it to area 12 to be melted down and recast.

15. Mecha-Halaster

Pillar Sconces. This hall has a 150-foot-high arched ceiling buttressed by stone pillars that have sconces protruding from them at 10-foot intervals. Continual flame spells cast on the sconces illuminate the hall.

Giant Construct. In the middle of the room, lying on its back on the stone-tiled floor, is a 100-foot-tall figure made of molded iron, its feet pointing toward the double door to the south. The construct is missing its head, and there are gaps in its outer shell through which the construct’s inner supports and mechanisms can be glimpsed.

Emberosa. This female fire giant has 221 hit points and the innate magical ability to hurl fire at will (as the fire giant’s Rock attack option, except it deals fire damage). She stands on the construct’s chest, 20 feet above the floor. Flitting around her are her sidekicks, three Smoke Mephit.

Pit. At the north end of the room is a 20-foot-deep pit with a dusty stone sarcophagus at the bottom.

Emberosa is inspecting the work of her fellow fire giants and doesn’t want to be disturbed. To say she has a temper would be an understatement. If intruders enter the hall, she tries to make quick work of them while her mephits taunt the new arrivals mercilessly. A battle here brings reinforcements rapidly from area areas 16 and 18.

The construct is made of recast bits of scrap iron plundered from Trobriand’s Graveyard (level 13). When complete, the construct will be the spitting image of Halaster Blackcloak himself—100 feet tall and made of iron. When the time comes to conquer Waterdeep, the Mad Mage plans to use Mecha-Halaster to destroy the city’s walking statues. Without its head and the immense magic needed to power it, the iron construct is nothing more than a giant boondoggle. In its current state, it is considered an inanimate object, not a creature. Medium or smaller creatures that squeeze inside it can use the outer shell and inner mechanisms as cover. Bigger creatures can’t fit inside the construct.

Pit and Sarcophagus

A character needs climbing gear or magic to scale the walls of the pit, which are made of smooth stone.

The sarcophagus at the bottom of the pit has a bas-relief of a laughing dwarf carved into its lid, the rim of which bears the following inscription in Dwarvish: “Here lies Lulz Klangphorn, trapsmith. He is survived by his work.” The lid can be pushed aside with a singular or combined Strength of 18. The sarcophagus contains nothing but dust, bones, and Lulz’s bronzed skull.

Removing Lulz’s skull from the sarcophagus causes mechanisms in the surrounding walls to grind and clank loudly, as though a complex trap has been set in motion. The effect, though harmless, is meant to frighten tomb robbers. After 1 minute, the noise stops.

16. Death’s Head Looters

Sarcophagi. Three dusty stone sarcophagi lie in a row in the middle of the room. Their flat stone lids have been pried off and cast aside.

Hobgoblins. Unless they have been drawn elsewhere, six Hobgoblin are rummaging through the sarcophagi.

Secret Door. A secret door in the north wall opens into area area 17. (The hobgoblins are unaware of the door.)

The hobgoblins, searching aimlessly for anything valuable, gang up on foes to quickly take them down.

Each sarcophagus contains the desiccated corpses of 1d3 humanoids in scorched robes, lying atop the dust of the ancient dead. The corpses are those of Arcturia’s past apprentices and assistants, each of whom displeased her in some way and paid the ultimate price.

17. Hidden Storeroom

This chamber is hidden behind secret doors and choked with dust and cobwebs. It has the following features:

Casks. Five heavy carrying-casks (barrels 3 feet long and 2 feet in diameter with sturdy rope handles) are stacked in the middle of the room. The ale inside them turned to vinegar and evaporated long ago.

Crate. Next to the casks is a brittle crate containing sixty-six small brass oil lamps shaped like dragon heads with open, smiling jaws. Each lamp has a wick, but there’s no oil to be found.

Stool. A three-legged stool lies on its side in the northeast corner. The bones of a dead stirge are nearby.

18. Death’s Head Guard Post

Hobgoblins. Unless they have been drawn elsewhere, four Hobgoblin guard this room. They gang up on foes, trying to take them down quickly.

Debris. Smashed wooden crates and furnishings piled along the walls are shrouded in dust and cobwebs.

Secret Door. A secret door in the south wall opens into area area 17. (The hobgoblins are unaware of the door.)

19. Storerooms

Hanging from the handles of the doors to these rooms are wooden signs that read “KEEP OUT!” in Common.

19a. Spell Component Storage

Stove. An iron stove stands against the south wall.

Coffers. Rows of dusty niches line the walls. Roughly half of the niches contain small wooden coffers.

The stove was given a semblance of life through an animate objects spell made permanent by a wish spell. It tears free of its stovepipe and charges forward on clawed feet to attack intruders.

The stove is a Large construct with a challenge rating of 3 (700 XP). It has AC 17, 50 hit points, a walking speed of 30 feet, and the following ability scores: Strength 14, Dexterity 10, Constitution 10, Intelligence 3, Wisdom 3, and Charisma 1. It has blindsight out to a range of 30 feet and is blind beyond this distance. It has the following action options:

Slam

Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 11 (2d8 + 2) bludgeoning damage.

Belch Fire (Recharge 4–6)

The stove belches fire in a 15-foot cone. Each creature in the area must make a DC 10 Dexterity saving throw, taking 22 (4d10) fire damage on a failed save, or half as much damage on a successful one.

Treasure

There are twenty-four wooden coffers in all, each one labeled in Common with the name of a spell and containing all the material components for one or more castings of that spell. The following table summarizes the coffers' contents:

19b. Inanimate Objects

Scattered about this room are inanimate objects that Arcturia animates using the animate objects spell:

• A brass brazier set atop a 3-foot-high tripod and a wooden broom (Small objects)
• A wooden coat rack; an iron torture chair festooned with spikes; a 10-foot-long, 250-pound chain; and a fat iron cauldron (Medium objects)
• A stone mine cart and a life-size, hollow bronze statue of a bull (Large objects)

20. Supplies

Two Hobgoblin are stationed outside this room, one in front of each door. Their orders are to guard the food supplies. A battle here alerts the hobgoblins in area area 32, who arrive quickly to aid their allies.

The room is packed with crates of rations and barrels of fresh water, with narrow aisles meandering between the containers. The giants and the hobgoblins rely on this supply, and there’s enough food and water to last for weeks.

21. Night and Day

Timekeeper. Four pillars support the 20-foot-high ceiling. An iron ring 20 feet in diameter is suspended from iron brackets affixed to the tops of the pillars so that it hangs parallel to the floor 20 feet below. Nested inside this ring is a circular iron disk of slightly smaller diameter with a symbol of the sun embossed on one side and a symbol of the moon on the opposite side. Directly above the ring and the disk is a 10-foot-deep, dome-shaped concavity in the ceiling.

Statues. Nestled in alcoves are two life-size statues of robed human wizards, their faces obscured under stony cowls and their arms raised toward the iron disk.

This room is one large timekeeping device. Every day at dawn and at dusk, the wizard statues exert invisible magical force upon the suspended iron disk, causing it to flip over within its circular frame like a coin. During the day, the sun symbol is visible on the disk’s underside; at night, the disk displays the moon symbol on its underside. When the disk rotates, half of it swings up into the dome-shaped concavity in the ceiling. The lower half swings downward, with 10 feet of clearance between its outer edge and the floor.

A detect magic spell reveals auras of evocation magic and transmutation magic around the statues, which defy all attempts to move or break them. If a creature attempts to turn the disk manually, the statues discharge lightning that fills the room. All creatures in the room at that moment must make a DC 18 Dexterity saving throw, taking 22 (4d10) lightning damage on a failed save, or half as much damage on a successful one. Creatures in direct contact with the iron ring or the disk, as well as creatures clad in metal armor, have disadvantage on the saving throw.

22. Arcane Scribblings

Chalkboards. Mounted on the walls are several blackboards on which arcane phrases and formulas are written in chalk.

Table Trap. A wooden table in the middle of the room bears a collection of dusty flasks and beakers. The table is draped in cobwebs and obviously hasn’t been disturbed in a long time. The paraphernalia is meant to distract viewers from the polymorph trap upon which the table rests (see “area Polymorph Traps").

The chalk scribblings were left by one of Arcturia’s failed apprentices. Any character who studies the markings and succeeds on a DC 16 Intelligence (Arcana) check can tell that they are attempts by one individual to unravel the secrets of spells beyond their comprehension. Spellcasters who have the disintegrate and flesh to stone spells on their spell lists can tell that those are the spells being researched, though neither spell can be learned from these incomplete scribblings.

Sounds of battle in this room can be heard by the hobgoblin guards in area area 25, who investigate if alerted. (They approach from the east.)

23. Experiments

The doors to these rooms have arcane lock spells cast on them that allow Arcturia alone to pass. A door can be forced open with a successful DC 25 Strength (Athletics) check.

23a. Shoe Hulk

Lying in the middle of this room is an old shoe with a scorpion hiding in it. If the shoe is disturbed, the scorpion scuttles out and attacks the nearest creature.

The scorpion is, in fact, an umber hulk under the effect of a polymorph spell made permanent with a wish spell. The umber hulk reverts to its true form and attacks when its scorpion form is reduced to 0 hit points.

23b. Bad Blades

A corroded steel helm rests atop a pile of rusty swords in the middle of the room. When another creature enters the room, the pile of swords gathers into a vaguely humanoid form with the helm surmounting it and attacks. This assemblage of rusty steel has the statistics of animated armor, except that its attacks deal piercing damage instead of bludgeoning damage.

23c. Rodent of Unusual Size

Monster. A giant two-headed rat (use death dog statistics) is trapped here. This rodent is the size of a human and is hostile toward all intruders.

Meat Chute. In the ceiling near the north wall is a rectangular opening, 12 inches long by 6 inches wide, that forms the mouth of a stone chute leading up.

Every few hours, a brick of rotting meat slides down the chute from a hidden chamber above. The meat hits the floor with a wet smack and is promptly eaten by the monstrous rodent. A Tiny or gaseous creature can access this small, hidden chamber by climbing up the chute. There are no exits from the upper room, which contains only hundreds of bricks of pink, rotting meat and a magical mechanism that pushes them down the chute at random intervals. It’s impossible to discern what sort of creature the meat has been harvested from.

23d. Guffaw the Stone Eater

This room contains the smashed remains of a dwarf statue and a plump deep gnome (svirfneblin) named Guffaw Gravelstock, who was plucked from his Underdark gem mine by Arcturia. He is unfamiliar with Undermountain.

Arcturia’s magic has given the gnome an insatiable appetite for carved stone. He uses his war pick to break up the statue and is devouring it slowly, one piece at a time. He can’t keep himself from stopping to eat any carved stone he sees—and there’s no end to how much he can consume. He begs to be left alone so he can finish his meal in peace. A successful dispel magic spell (DC 19) cast on Guffaw rids him of his unique magical malady.

Treasure

The instant he is cured of his malady, Guffaw coughs up two diamonds (5,000 gp each). He is just as surprised to see the gemstones as anyone else, and he offers them to the characters as a reward for “saving” him. He then seeks out a way back to the Underdark, wanting nothing more to do with Undermountain.

24. Empty Classroom

Chalkboard. A blackboard covers the entire east wall. Written across it in big chalk letters are the words “YOU ALL FAIL!” in Common.

Desks. Whenever a creature enters the room, seven stone desks magically rise from the floor, facing the blackboard in an arc. (The desks sink back into the floor when all creatures leave the room.)

Secret Door. A secret door in the south wall pushes open to reveal a dusty, web-choked passage between this room and area area 25.

25. Hobgoblin Guards

Guards. Two Hobgoblin stand guard here, one in front of each door. They attack intruders, ganging up on one enemy at a time.

Arch. A stone arch embedded in the middle of the east wall has an image of an open book carved into its keystone.

Secret Door. A secret door in the north wall opens into a dusty, web-choked passage between this room and area area 24.

Arch Gate to Level 9

The arch is one of Halaster’s magic gates (see “Gates”). Its rules are as follows:

• Holding an open book while standing within 5 feet of the arch causes the gate to open for 1 minute. The book turns to dust as the gate opens, even if it is a spellbook.
• Characters must be 10th level or higher to pass through this gate (see “area Jhesiyra Kestellharp"). The first creature to pass through the gate triggers an elder rune (see “area Elder Runes").
• A creature that passes through the gate appears in area area 49 on level 9, in the closest unoccupied space next to the identical gate located there.

26. Apprentice’s Quarters

Like her former master Halaster, Arcturia takes on apprentices of her own from time to time, but they seldom survive for long. This room contains a moldy quilt draped over a stone bier against the north wall and a wooden desk with a high-backed chair in the southeast corner. On one corner of the desk rests a yellowed human skull topped with a half-melted wax candle.

27. Dead Apprentice

Quilt. A moldy quilt is draped over a stone bier against the south wall.

Desk. A wooden desk stands in the northeast corner. Slumped in a high-backed chair behind the desk is a human skeleton clad in perforated black robes.

The inanimate skeleton belongs to a human apprentice named Kazvark, whom Arcturia killed with a barrage of magic missiles for failing to complete a simple homework assignment. Arcturia destroyed Kazvark’s spellbook but didn’t check his pockets for valuables.

Mithral Key

Characters who search the apprentice’s robes find a 6-inch-long, flat piece of mithral shaped like a U in one pocket. This key is one of six required to activate the weapon of mass disintegration in area area 37.

28. Specimens

Characters who listen at either door to this room hear strange clicking noises from beyond.

Hook Horror. A hook horror is trapped in the room, but there’s more to it than meets the eye.

Shelves. The curved walls are lined with stone shelves.

Smashed Jars. Hundreds of jars of body parts lie smashed on the floor.

A hobgoblin accidentally set off a polymorph trap and was transformed into this hook horror. The other hobgoblins decided to trap it in this room as a joke. Lacking hands, the hook horror couldn’t open the doors to escape, and it swept the bottles off the shelves in a rage, spilling their contents.

When the hook horror drops to 0 hit points, it turns back into an unconscious hobgoblin named Jarrk. Despite his recent misadventure, Jarrk is fanatically loyal to Doomcrown and would never willingly betray him.

Arcturia collected body parts from all sorts of Underdark specimens. Characters who search through the detritus find moth wings, beetle shells, darkmantle eyes, stirge hooks, flumph tendrils, troglodyte claws, demon ichor, gelatinous residue, and other worthless creepy bits. At your discretion, some useful spell components might lie amid the refuse.

29. Laboratory

Vanar Freth. A drow mage named Vanar Freth and his summoned shadow demon companion are quietly searching the room when the characters arrive.

Statues. Standing in opposite corners are two 9-foot-tall statues of ogres transforming into giant flies.

Table. A large stone table stands in the middle of the room. Several curious items rest atop it, including a black cube-shaped box on a folded gray blanket, and the slimy, decapitated head of a mind flayer whose headless body has bled out on the floor nearby. The corpse is being feasted on by maggots.

Old Trap. The double door to the southwest and the floor around it are scorched by fire—the result of a trap set off long ago.

The drow mage has managed to get this far without being detected. Left to his own devices, he eventually finds the treasure hidden under the table (see “Treasure” below). The shadow demon watches for trouble while the drow busies himself with the search.

Vanar fights to keep any treasure he has found but otherwise avoids hostilities. Once his search of Arcturiadoom is complete, he plans to return to the House Freth fortress on level 12 and report to his master, Drivvin Freth.

Table

Until recently, Arcturia had a mind flayer assistant. She tore off its head to study the psychic energy stored in its brain. Next to the head is a long pair of steel tweezers and a ladle.

The 1-foot black cube is an ebony-framed box fitted with panes of black glass. The box has a hinged lid and radiates an aura of transmutation magic under the scrutiny of a detect magic spell. When a Tiny beast small enough to fit in the box (such as a rat or a lizard) is placed inside and the lid is closed tightly, the box magically transforms it into some other Tiny beast (your choice) unless it succeeds on a DC 15 Wisdom saving throw. The box can do this eight more times before its magic is fully spent, whereupon it crumbles to sand.

The folded gray blanket upon which the box rests is, in fact, the carefully removed skin of a doppelganger. Other items on the table include a jar of cockatrice tongues, a block of soft clay (the material component for the stone shape spell) wrapped in moist cloth, and a wooden coffer labeled “Polymorph” containing a dozen caterpillar cocoons (material components for the polymorph spell).

Treasure

Hidden in the floor under the table is a small secret compartment that can be discovered with a successful DC 20 Wisdom (Perception) check. It contains a jade circlet worth 1,500 gp (the material component for a shapechange spell) and a spell scroll of polymorph.

30. Hideous Transmutation

Carrion Ogre. Lying on the floor in the middle of the room, held down with chains, is a creature that has the body of an ogre and the head of a carrion crawler.

Body Parts. The ogre’s severed head and the carrion crawler’s decapitated body lie discarded in the northern corner of the room, where they have begun to putrefy and emit a dreadful stench.

Key Ring. Hanging from a stone peg on the northwest wall is an iron ring with three keys.

The creature chained to the floor is alive, having survived a ghastly magical ritual that can’t be reversed or undone. It is malnourished and must feed on carrion to survive. The chains around it are looped through iron rings bolted to the floor and secured with three heavy padlocks, which can be unlocked with the keys hanging on the wall. If released, the creature rushes over to the rotting remains of its former bodies and begins devouring them.

The creature is an ogre, with these changes:

• While lashed to the floor, the creature is prone and restrained. It also suffers from two levels of exhaustion.
• It has an Intelligence of 1, and it can’t speak or understand any language.
• Replace the ogre’s action options with the following action options.

Multiattack

The creature makes two attacks: one with its tentacles and one with its bite.

Tentacles

Melee Weapon Attack: +8 to hit, reach 10 ft., one creature. Hit: 4 (1d4 + 2) poison damage, and the target must succeed on a DC 13 Constitution saving throw or be poisoned for 1 minute. Until this poison ends, the target is paralyzed. The target can repeat the saving throw at the end of each of its turns, ending the poison on itself on a success.

Bite

Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 7 (2d4 + 2) piercing damage.

31. Illithid’s Assistant

This room was reserved for Arcturia’s mind flayer assistant, which met a grisly end in area area 29. It has the following features:

Decor. The stone walls are sculpted to resemble tentacles entwining around and through bleached human skulls embedded in the stone.

Slime Pool. In the middle of the floor is a shallow oval pool filled with dark, foul-smelling slime. (The slime has a soothing effect on mind flayers but no magical properties to speak of.)

Assistant. Standing in the eastern corner of the room, facing the corner, is a male human wearing nothing but a leather harness and a loincloth.

The harness-wearing human is Ellix Gaspar (NE male Tethyrian human mage with no spells prepared). He holds a half-eaten loaf of bread. Arcturia pulled him out of Dweomercore (level 9) a few months ago to serve as her assistant, only to find him too obnoxious to bear. She cast a feeblemind spell on him and gave him to her mind flayer assistant, who promptly forced him to don new apparel befitting his station.

In his current state, Ellix is vacant-eyed and barely responsive, with a tendency to trip over his own feet and drool uncontrollably. He has a tenday left before he can attempt another saving throw to end the feeblemind effect. If he regains his senses, he smartly tries to flee Undermountain with the last shreds of his sanity and dignity. He doesn’t know what happened to his spellbook (Arcturia hid it in area area 40b), but once his faculties return, he recalls the layout of this level and how to return to the surface.

32. Death’s Head Barracks

Hobgoblin forces are quartered in these rooms, which are engulfed in a permanent antimagic field similar to that created by an antimagic field spell (the result of a magical experiment gone awry).

32a. Soldiers' Quarters

Thirty Hobgoblin rest in wooden bunk beds stacked three tiers high. There are enough beds to accommodate sixty guards. The hobgoblins sleep in their armor; their weapons and shields hang from hooks on the corners of their bunks.

32b. Guard Post

Four Hobgoblin stand guard here—two flanking the door to area area 32a, and two flanking the door to area 32c. Any battle here brings reinforcements from those areas, as well as from area area 20.

32c. Captains' Quarters

Two Hobgoblin Captain converse quietly in this room, which contains three beds. Other furnishings include a stone table surrounded by six wooden stools, with an unlit iron chandelier suspended above it.

The captains are worried about the recent abnormal behavior of their warlord commander (see area 33) and contemplating what to do about it. So far, the captains have hidden Doomcrown’s bizarre preoccupations from the rest of the hobgoblin legion and remain, for the time being, loyal subordinates.

33. Doomcrown’s Quarters

Monsters. If he hasn’t been drawn elsewhere, Doomcrown the hobgoblin warlord is here, attended by a flumph that speaks to him telepathically.

Underdark Model. Standing about the room are six 7-foot-tall, stalagmite-shaped spires made of tiny rectangular blocks, with a half-finished seventh tower under construction.

Furnishings. Furnishings include a wooden bed, an overstuffed leather chair with a matching ottoman, a stone shelf holding a wooden cask of ale, a handsomely carved stone table strewn with mason’s tools and bits of stone, and a heavy wooden seafarer’s trunk with a smashed lock.

Tapestry. On the south wall hangs an old, faded tapestry that depicts a beautiful crystal cavern.

A few days after settling in Arcturiadoom, the hobgoblin warlord commanded his underlings to bring him a set of mason’s tools. Some old tools were gathered and promptly delivered to him. In the days since, Doomcrown has been carving rectangular blocks of stone (each 2 inches wide, 4 inches long, and 1 inch thick) and using them to build odd, tower-like structures resembling stalagmites. The endeavor has helped alleviate his boredom, even if he doesn’t know exactly why he’s building them. The answer lies with his strange companion.

Until recently, this flumph surreptitiously fed on the mental energy of Arcturia’s mind flayer assistant. The illithid’s sudden death (see area area 29) cut off the flumph’s food supply. Fortunately, it can get by for some time without needing to feed on more psionic energy. It shacked up with Doomcrown and has been trying to convince him to reform. The hobgoblin has proven to be stubbornly, irredeemably evil, but their lengthy telepathic contact has caused Doomcrown to exhibit odd traits, including a subconscious need to recreate the flumph’s home—the Underdark—out of building blocks. The flumph knows that its longing to return home is affecting the hobgoblin’s behavior, but it relies on Doomcrown for protection. If the two become separated, the flumph opts to return to the Underdark.

The characters can befriend the flumph and coax it into joining the party for a while. It has encountered adventurers in Undermountain before and is generally quite fond of them and their tales of the surface world.

Treasure

The wooden trunk contains the hobgoblins' loot: 2,500 gp, an electrum pepper shaker (25 gp), a pewter candlestick (25 gp), a red velvet cape (50 gp), an ornate coral statuette of a ship cresting a wave (250 gp), a dwarven beard comb made of lapis lazuli and set with gemstones (750 gp), a platinum crown with black pearl inlay (2,500 gp), and an elven helm made of leafed gold with a spiral horn of amethyst protruding from its brow (7,500 gp).

34. Shrieking Gas Spore

Floating in the middle of this otherwise empty room is a gas spore that has the added defense of a shrieker. When bright light or a creature comes within 30 feet of the gas spore, it uses its reaction to emit a shriek audible within 300 feet of it. The gas spore continues to shriek until the disturbance moves out of range and for 1d4 rounds afterward.

The shrieking of the gas spore alerts the hobgoblins in area areas 32c and area 33, who come to investigate.

35. Rallying Hall

This wide hall has a 50-foot-high ceiling that angles down to 20 feet high as it travels north and east. Shouts echo from area 36, the door to which is slightly open.

36. Death’s Head Training

The door to this room hangs ajar, and shouts in Goblin come from within. The room contains the following features:

Hobgoblins. Twelve Hobgoblin are practicing phalanx formation maneuvers in the middle of the room, overseen by a hobgoblin captain. When faced with an unknown threat, the hobgoblins close ranks and attack.

Furnishings. Around the perimeter of the room are wooden trestle tables and benches.

Wall Decor. The room is lit by continual flame spells cast on iron torch sconces bolted to the walls. Mounted on stone plaques between the sconces are the heads of three dwarves, two orogs, a troglodyte, and a gargoyle.

37. Weapon of Mass Disintegration

In the event that her experiments got out of hand or her enemies tracked her down, Arcturia built this chamber to purge them all at once while protecting herself and her apprentices (of which she currently has none). The chamber has the following features:

Plated Walls. At the end of a short hallway is a 20-foot-high domed chamber with seven narrow alcoves. Every surface is covered with gleaming mithral plates. Each alcove is brightly lit by the yellow glow of a small crystal dome embedded in its 8-foot-high ceiling.

Key Shapes. Set into the mithral-plated walls between the alcoves are six key-shaped indentations at chest height. Each indentation is 6 inches long.

Each alcove is 8 feet tall and 4 feet deep, and narrows in width from 3 feet to 1 foot. A detect magic spell reveals a strong aura of abjuration magic engulfing each alcove, which is just spacious enough to accommodate a single Medium creature. The crystal dome in the ceiling is the source of the alcove’s magic, and destroying its globe renders an alcove dark and powerless. Each dome has AC 11, a damage threshold of 10, 1 hit point, and immunity to acid, fire, poison, and psychic damage.

Using the Mithral Keys

Six mithral keys are required to activate the chamber. Each conforms in shape to one of the six indentations in the walls, which are (from left to right, going clockwise around the room): an upside-down Y, a backward J with a small loop at the top, an upside-down F, an upside-down U, a V with a small loop at the bottom, and an H missing its top left stem. When the six keys (located in area areas 7, area 10, area 13b, area 27, and area 39a) are placed in their corresponding indentations, a magic mouth spell counts down from 20 seconds (in Common). At the end of the countdown, there is an ear-splitting whine, and a powerful spell deals 150 force damage to every creature on level 14 of Undermountain (no saving throw allowed). Any creature reduced to 0 hit points by this effect is immediately disintegrated and reduced to a pile of dust. The spell also disintegrates the six mithral keys.

Creatures that are standing in the lit alcoves when the spell goes off are unharmed, as are creatures inside an antimagic field. (The antimagic fields in area areas 4 and area 32 protect the creatures there.)

38. Guest Quarters

Arcturia keeps this room for special guests, such as Halaster or visiting wizards who have magic to trade. Its features are as follows:

Furnishings. A large canopied bed dominates the eastern alcove. At the foot of the bed rests a large iron chest with a flat lid and clawed feet. An owlbear rug is splayed across the floor in front of the chest and the bed.

Alcove. A black curtain conceals an alcove to the southwest. In front of the curtain is an overstuffed leather chair and a small table with a crystal decanter.

The alcove contains a stone statue that lacks fine features, resembling a blank-faced humanoid. A detect magic spell reveals an aura of transmutation magic around the statue, which alters its form to mimic the appearance of any Small or Medium humanoid that touches it. The statue has no other properties.

Trapped Chest

The chest has an iron key in its lock, and turning the key unlocks it. A detect magic spell reveals an aura of transmutation magic emanating from inside the chest.

The chest is empty except for a magic mirror fastened to the inside of its lid. Any creature that sees its reflection in the mirror is targeted by a flesh to stone spell (save DC 20). Once the spell has been triggered, the mirror ceases to be magical.

Treasure

The crystal decanter is worth 250 gp but is fragile. It contains cheap wine. The owlbear rug is worth 75 gp.

39. Arcturia’s Boudoirs

Mounted above the double door to these chambers is a 4-foot-diameter, 2-inch-thick disk of black stone upon which is engraved a white symbol depicting a bony human hand. A detect magic spell reveals a powerful aura of abjuration magic around the seal.

The seal has AC 17, 30 hit points, and immunity to poison and psychic damage. If the seal is destroyed, the rakshasa bound to these chambers can escape.

39a. Gold and Black Boudoir

Light. The walls and ceiling are painted gold. Mounted to them are black iron sconces with continual flame spells cast on them. These fires cast the entire room in bright, flickering light.

Carpet and Cushions. Thick, wall-to-wall carpeting with alternating gold and black zigzagging patterns covers the floor, with a few soft, gold silk cushions strewn about.

Hammocks. Two tasseled hammocks are stretched between four black pillars near the east wall. Napping in one of them is a beautiful young man wearing gold sandals and a golden silk skirt. (The man is Alussiarr, a rakshasa using a disguise self spell to mask its true form.)

Braziers. Two braziers made of carved black basalt rest in the middle of the floor. Smoldering blocks of incense in each brazier fill the room with a pungent but pleasant aroma.

The rakshasa is bound to these boudoirs and can’t travel beyond area area 39, even through the use of spells, as long as the circular seal above the doors remains in place. (Spells that would transport the rakshasa away from the area simply fail.) Arcturia trapped the rakshasa here years ago and draws blood from the fiend to fuel her terrible transmutation rituals.

Alussiarr has no beef with the adventurers and doesn’t want to distress them by revealing its true form. It does, however, ask them to set it free by breaking the seal outside the room. If the characters do so, the rakshasa turns invisible and makes its way out of Undermountain with the goal of working all manner of evil in Waterdeep—but not before telling the heroes where they can find Arcturia’s spellbook (area area 40b) and phylactery (area area 40c), as well as the command word to reveal the bookshelves in area area 40b. It also gives them a flat, 6-inch-long mithral key shaped like a Y, and tells them it’s one of six keys required to activate the weapon of mass disintegration in area area 37. Alussiarr doesn’t know where the other five keys are kept.

If the characters haggle with the rakshasa, it also vows to provide up to three additional pieces of useful information in exchange for its freedom, such as the way to level 15. If the characters refuse to help Alussiarr, the rakshasa shrugs its shoulders, returns to its nap, and gives them nothing in return. It has waited years to escape—it can wait a few more.

39b. Skull and Bone Boudoir

Mosaics. Gruesome mosaics made from humanoid bones decorate stone-framed panels set into the walls.

Furnishings. Arrayed about the room are six divans made of stitched flesh stretched over bone frames and a table made entirely of glued teeth and fangs.

Arch. Set into the middle of the south wall is a stone arch. Carved into its keystone are three human-like stick figures holding hands.

Arch Gate to Level 17

The arch is one of Halaster’s magic gates (see “area Gates"). Its rules are as follows:

• If three humanoids hold hands while standing within 5 feet of the gate, it opens for 1 minute.
• Characters must be 14th level or higher to pass through this gate (see “area Jhesiyra Kestellharp"). The first creature to pass through the gate triggers an elder rune (see “area Elder Runes").
• A creature that passes through the gate appears in area area 11 on level 17, in the closest unoccupied space next to the identical gate located there.

39c. Crystalight Boudoir

Chandeliers. Four crystal chandeliers hang from the ceiling, bathing the chamber in magical light.

Harpsichord. A living unseen servant (see appendix A) plays a harpsichord in the southeast corner. Because the unseen servant is invisible, the harpsichord seems to be playing by itself.

Dancers. Waltzing about the room are a resplendently dressed man and woman. The man wears a gold ruffled shirt and blue trousers, while the woman wears a ruffled blue ball gown and a gold tiara.

The living unseen servant plays the harpsichord tirelessly and fights only in self-defense.

A detect magic spell reveals auras of transmutation magic around the dancers who, in truth, are a mated pair of Young Blue Dragon. The dragons are Arcturia’s guests, and their names are Nystalancer and Venasorrn. With the help of Arcturia’s magic, they are experiencing what it’s like to be human and pay no attention to new arrivals. If the music stops or either of them is touched or harmed by another creature, the dragons revert to their true forms simultaneously and attack. Their clothing and jewelry merge into their new forms. Arcturiadoom is not their lair, and they keep no treasure here.

40. Arcturia’s Chambers

Arcturia has cleared out an old dwarven crypt and turned it into her private sanctum.

40a. Sentinel Statue

Statue. Standing in the middle of this 30-foot-high room is a life-size statue of a dwarf in plate armor, wearing a bucket helm and standing at attention atop a block of stone that measures 3 feet on a side.

Secret Door. Set into the north wall is a secret door that swings open into area 40b.

The dwarf statue is inseparable from its base, and its base is inseparable from the floor. If anyone other than Arcturia opens the secret door, the statue transforms into a 6-inch-thick wall of stone that bisects the room from east to west, creating separate chambers to the north and south. The wall is permanent. Each 10-foot-square section of it has AC 15, 180 hit points, and immunity to poison and psychic damage.

40b. Arcturia’s Library

Pedestal. A 5-foot-tall stone pedestal carved in the likeness of a nalfeshnee demon stands near the southern wall.

Secret Door and Trap. A secret door in the east wall opens into area 40c. The 10-foot-square space in front of the secret door contains a polymorph trap (see “area Polymorph Traps").

A detect magic spell reveals auras of transmutation magic around the pedestal and rectangular sections of the north wall where hidden bookshelves magically emerge (see “Treasure” below).

The pedestal is a Small object with AC 15, 20 hit points, and immunity to poison and psychic damage. Under certain conditions, it transforms into a nalfeshnee (see area 40c). The pedestal also transforms if it takes damage. With Halaster’s help, Arcturia pressed the demon into service. Its primary task is to guard the lich’s phylactery. While in pedestal form, the demon is unaffected by the weapon of mass disintegration in area area 37.

Treasure

When the proper command word is spoken (“palimpsest”), tall stone bookshelves magically protrude from the north wall. The shelves are inaccessible otherwise. Packed into these shelves are dozens of spellbooks that Arcturia has accumulated over the years. They contain most of the wizard spells in the Player’s Handbook, plus any others of your choosing.

All the 8th-level and 9th-level spells that can be found are contained in Arcturia’s personal spellbook, which magically changes its appearance each dawn. When first discovered, it has black crystal covers and gold-leaf pages engraved with arcane runes and phrases. The book is titled Arcturia’s Arcane Esoterica: Vol. IX, and it contains the following spells: antimagic field, astral projection, dominate monster, feeblemind, gate, incendiary cloud, power word kill, power word stun, shapechange, telepathy, true polymorph, and wish.

40c. Arcturia’s Phylactery

A niche in the north wall holds a small box made of purple crystal—Arcturia’s phylactery. The phylactery does not detect as magical. If the characters remove the phylactery from this room, the demonic pedestal in area area 40b transforms into a nalfeshnee and attacks them.

Destroying this phylactery leaves Arcturia with no means to rejuvenate once her physical form is destroyed. The object can be destroyed only after being digested in the stomach of a mimic for three days. A legend lore spell or similar magic reveals the exact method of the phylactery’s destruction.

41. Watchful Pillars

Two stone pillars, each carved with dozens of lidless eyes facing in all directions, flank a double door.

The doors swing inward, revealing a 10-foot-wide landing at the top of a staircase that descends hundreds of feet to area level 15, area 1.

Aftermath

Arcturia returns to her home periodically to peruse her spellbooks, place new polymorph traps throughout the level, and alter the conditions that trigger existing ones, as needed. If intruders have laid waste to her defenses, she might forge an alliance with the mind flayers on area level 17, intending to secure an illithid security force to further strengthen her hold on this level. If the dragons in area area 39c are still alive, Arcturia bribes them into guarding the tunnels leading to levels 13 and 15.

Defeating Emberosa and her giants stalls the progress on Mecha-Halaster, but only until Halaster finds new metalsmiths (perhaps a band of azers) to continue the work. The Mad Mage considers the hobgoblins expendable.