Halaster makes his home in the lowest level of Undermountain, which is optimized for four characters of 17th level or higher. Characters who defeat the monsters on this level should gain enough XP to reach 20th level.
Who Dwells Here?
In addition to Halaster, two of the Mad Mage’s apprentices reside on this level: Arcturia and Trobriand.
Halaster Blackcloak
If the adventurers have made their way to this level, Halaster is equal parts impressed and curious. He is ready to grant the characters an audience, having kept an eye on their progress. True to the nature that earned him the moniker “Mad Mage,” Halaster’s demeanor toward the characters can change on a whim. He might alternate between seeming furious, baffled, annoyed, amused—or simply bored, depending on what the characters have accomplished before reaching this level. See appendix A for more information on the Mad Mage.
If the characters and their actions support Halaster’s current goal (see “area Halaster’s Goals"), the Mad Mage is not necessarily hostile. For example, if his primary goal is to find an apprentice, Halaster has kept an eye on any arcane spellcasters in the party. He might suggest that those characters prove their worth by surviving the Mad Wizard’s Lair and “freeing up” an apprenticeship by eliminating Arcturia or Trobriand. If this is done, Halaster is willing to take on an appropriate character as a new apprentice. Halaster has no sentimental attachment toward his apprentices, and he often enjoys secretly tormenting them.
Arcturia
Arcturia is a lich and a master of transmutation magic. She has altered her form dramatically over the years, now appearing more alive than undead. Gossamer wings sprout from her shoulders, and bone spurs jut from her forearms and elbows.
If the characters destroyed her phylactery on area level 14, Arcturia attacks them on sight. She has no beef with them otherwise.
Trobriand the Metal Mage
Trobriand specializes in the creation of magical constructs. Characters who have passed through the upper levels might have encountered some of his creations.
Fed up with the frailty of the flesh, Trobriand has transferred his spirit into the body of a specially prepared iron golem. This merging of spirit and metal has done nothing to improve his sanity, however.
The Dungeon
Locations in the dungeon portion of this level (areas 1 through 21) are keyed to map 23. No tunnels or staircases connect this dungeon complex to the upper levels of Undermountain. Characters arrive in area area 1 after passing through a gate in Shadowdusk Hold (area area 35 on level 22).
1. No Retreat
Arch. The north wall is set with a stone arch, its keystone bearing Halaster’s visage whose animated eyes follow any creature that approaches the arch. Carved into the wall above the keystone is a sigil.
Statue. An alcove to the south contains a life-size, painted stone statue of Halaster perched atop a 4-foot-tall granite plinth like a vulture, squatting with arms outstretched and fingers curled like talons, as though ready to leap down and claw at anyone who stands before it (see “area Halaster Statue” below).
Frescoes. Six 10-foot-square painted frescoes adorn the walls around the arch: two flanking the arch on the north wall, two side by side on the west wall, and two side by side on the east wall. Each fresco displays a magically animated image of Halaster performing one or more mundane activities: stretching and yawning, juggling rods, sweeping the floor with a broom, trying to escape from a straitjacket, doing handstands, and shadowboxing.
Secret Door. Hidden behind the fresco that depicts Halaster stretching and yawning is a secret door.
Targeting an animated fresco with a
Arch Gate to Level 22
The sigil inscribed above the arch is Halaster’s personal rune. Both it and the face carved into the keystone are harmless.
Halaster can open the gate for 1 minute by touching the arch. The gate cannot otherwise be opened from this side. A creature that passes through the gate appears in area area 35 on level 22, in the closest unoccupied space next to the gate located there.
Halaster Statue
Anytime a creature other than Halaster tries to cast a spell in this room, the statue’s arms animate and perform the quick series of somatic gestures needed to cast
The statue is a Large object with AC 17, 50 hit points, and immunity to all damage except force damage. The statue falls to pieces and loses its spellcasting ability if it is reduced to 0 hit points. Destroying the statue triggers a
2. Reversed Library
Everything in this room is upside down because gravity in the room is magically reversed. The room is furnished thusly:
Bookshelves. The walls are lined with upside-down bookshelves, fully stocked with upside-down history books from the many parts of the world Halaster has explored.
Desk. In the middle of the 15-foot-high ceiling is an upside-down desk topped with a stack of tomes held between two golden, upside-down bookends shaped like bulettes bursting out of the ground.
The reverse gravity field can’t be negated, though it is suppressed within an antimagic field. Unless anchored, held down, or affected by a
The desk is empty except for the array of nine books held between the bulette-shaped bookends. Eight of the books contain essays pertaining to the eight schools of magic, one book dedicated to each school. The cover and the pages of the ninth book appear blank.
Placing the other books in alphabetical order by school of magic between the bookends causes Halaster’s rune to appear on the cover of the ninth book and spells to appear on its pages. This tome is one of Halaster’s spellbooks (see “Treasure” below).
Treasure
The gold bookends are worth 500 gp for the pair, while the eight books detailing the schools of magic are worth 100 gp each.
Halaster’s spellbook contains the following spells:
3. Talking Heads
This 10-foot-high room has wooden shelves covering the walls from floor to ceiling. Hundreds of wide-mouthed jars line the shelves, each containing a severed head floating in brine.
The heads in the jars are specimens that Halaster has collected throughout Undermountain: goblins, drow, kuo-toa, duergar, troglodytes, githyanki, mind flayers, and other creatures. Although detached from their bodies, the heads remain alive and sedate as a result of Halaster’s magic. Tapping on a jar is enough to stir a head to consciousness. The heads speak only the languages they knew in life and have no recollection of how they ended up in their disembodied state. A character can prompt a head for information, which it’s happy to provide. Each head shares one Undermountain secret determined by drawing a card from the Secrets Deck (see appendix C). A head can also confirm that Halaster spends a lot of time on this level of Undermountain.
Removing a head from a jar or removing a jar from this room ends the magic that animates the head, which immediately dies.
4. Helmed Horrors
Six Helmed Horror float in the alcoves marked H on map 23. These constructs attack intruders on sight and fly after those who flee.
5. Magical Repository
Ceiling. This room has a 30-foot-high vaulted ceiling.
Statues. Four statues, each one carved to look like a 20-foot-high purple worm bursting up through the floor, fill the corners of the room. (These statues are harmless.)
Dome. A deep, 20-foot-high alcove in the north wall contains four Invisible Stalker trapped inside an invisible, dome-shaped wall of force rising from the floor. (Any items that Halaster removed from the mine carts in area level 15, area 1, lie on the floor inside the dome. The dome appears to contain nothing else.)
The dotted circle on map 23 marks the edge of the dome, which was created by a
The invisible stalkers attack any creature other than Halaster that enters the dome using magic (such as a
6. Wizardly Wards
A trapped hall (area 6a) guards two of Halaster’s vaults (areas 6b and 6c).
6a. Lightning Pillars
This two-chambered hall has a 20-foot-high ceiling supported by ten copper-plated pillars of iron. The pillars generate arcs of magic lightning, as well as bolts that leap from one pillar to another. Creatures standing outside the hall are safe, as are creatures within the 20-foot-square space marked on map 23. A creature that ends its turn in any other space in the hall is struck by lightning from the nearest pillar and must make a DC 15 Dexterity saving throw, taking 22 (
A character who uses an action to study the pillars and succeeds on a DC 20 Intelligence (
6b. Angelic Shield
Mounted on the door to this chamber is a bronze knocker shaped like Halaster’s mad visage, his beard entwined around the knocker’s ring-shaped handle. A tiny bronze plaque mounted below the knocker reads in Common, “Knock first before entering.”
Using the knocker triggers a
Shield
The room is empty except for a steel shield hanging on the south wall. The shield is cast in the form of a serene, angelic visage wreathed in bronze feathers.
A
If an
While trapped in the shield, the pit fiend can communicate telepathically with the shield’s wielder. It pretends to be a sentient magic item that is unwilling to disclose its secrets, trying to goad the characters into casting
6c. Components Storeroom
This room contains wooden trestle tables laden with material components for spells, including linen-wrapped slabs of butter, casks of licorice root shavings, bottles of snake tongues, a terrarium filled with glowworms, and wax-sealed jars of rotting eggs.
7. Teleportation Pillars
Eight black marble pillars form a circle in this 20-foot-high room. Carved into each pillar is a symbol representing one of the eight schools of magic (Abjuration, Conjuration, Divination, Enchantment, Evocation, Illusion, Necromancy, and Transmutation).
The first time a character enters the circle of pillars, a
A crown festooned my dwarven brow.
I rest beneath the mountain now.
Who am I?
The answer is “Melair,” the dwarf king who is buried on level 6. The characters can use divination magic to determine the correct answer if they can’t work it out.
Speaking Melair’s name aloud while standing in the room causes the symbols on the pillars to glow bright colors. The symbols continue to glow for 1 minute. During that time, any creature that enters the area inside the pillars or starts its turn there is teleported to a similar location in area area 8, along with anything it is wearing or carrying.
8. Teleportation Pillars
Eight black marble pillars stand in a circle near the walls of this 20-foot-high room. A fist-sized yellow sapphire is embedded in each of the five easternmost pillars at a height of 10 feet, such that all five gemstones face inward. Each of the remaining three pillars, in the west side of the room, bears an empty indentation where a similar gem is meant to be placed. The three missing gems can be found in area area 17.
When all eight yellow sapphires are placed in their pillars, they glow brightly as the pillars' magic activates. Any creature that enters the area inside the pillars or starts its turn there is teleported to a similar location in area area 7, along with anything it is wearing or carrying.
The sapphires can be pried from their fixtures, but removing even one of them deactivates the pillars.
Treasure
The yellow sapphires are worth 1,000 gp each.
9. Vaults
These chambers have 15-foot-high, flat ceilings.
9a. Hall of Staffs
Mosaics. Tiled mosaics depicting a variety of magic staffs cover the walls. (Hidden behind a mosaic depicting a
staff of thunder and lightning is a secret door.)Dead End. Part of the eastern wall has been obliterated, leaving behind a jagged dead-end tunnel.
The mosaic of the
9b. Diabolical Shield
Hanging on the west wall of this otherwise empty 15-foot-high room is a steel shield cast in the form of a scowling devil’s face wreathed by bronze flames.
A
Aryx was sent by Tyr, the god of justice, to talk some sense into Fazrian, the fallen planetar on level 21. Before Aryx could approach Fazrian, however, Halaster trapped the deva in the shield. Aryx must complete its mission before it can return to Tyr’s heavenly realm. If the characters claim to have killed Fazrian or helped the planetar achieve atonement, the deva uses a
10. Arcane Display
These areas have 20-foot-high, arched ceilings.
10a. Zigzagging Gallery
Characters who make a loud racket in this hall attract the seven Flameskull in area area 10b. The features of this hall are as follows:
Chandeliers. Radiant crystal chandeliers levitate near the ceiling.
Paintings. Paintings line the walls. They come in many sizes and have gilded frames.
The hall contains three chandeliers, their locations marked on map 23. Each chandelier magically sheds bright light in a 20-foot radius and dim light for an additional 20 feet. A chandelier can bear up to 150 pounds of additional weight before falling. Casting
The paintings are stuck to the walls with
10b. Shield Trap
Flameskulls. Unless they were drawn to area area 10a, seven Flameskull float here, their green flames the only sources of light in this room.
Decor. More paintings like the ones in area area 10a line the walls. A golden shield encrusted with gemstones hangs on the south wall among the paintings.
Halaster made the flameskulls from the skulls of wizards who tried and failed to become his apprentices. They attack intruders on sight, bombarding them with
Hanging on a stone peg that juts from the wall, the gold-plated shield is etched with arcane runes. A
Any creature that touches the shield must succeed on a DC 18 Wisdom saving throw or become trapped inside it, along with everything the creature is wearing or carrying. The shield displays a faint image of the trapped creature in its reflective outer surface. The shield can trap only one creature at a time. Whenever it traps a new creature, the shield releases its current prisoner, which appears in an unoccupied space as close to the shield as possible.
A creature trapped in the shield can do nothing except attempt a DC 18 Charisma saving throw at the end of each of its turns. On a successful save, the creature is released and appears in an unoccupied space as close to the shield as possible. On a failed save, the creature takes 31 (
Treasure
The shield is worth 7,500 gp and can be used as an ordinary shield, but battle damage might reduce its value as an art object at your discretion.
11. Trobriand’s Workshop
These areas have 20-foot-high, flat ceilings.
11a. Work in Progress
Scrap Metal. Workbenches lining the east and west walls are covered in metal scraps.
Unfinished Construct. In the center of the room is a Huge scorpion constructed from metal. (This is an incomplete scaladar that is not active.)
11b. Scaladar
Guards. Two scaladar (see appendix A) guard this room and won’t leave it under any circumstances.
Secret Door. The walls, floor, and ceiling are covered in 5-foot-square steel tiles. One tile conceals a secret door in the east wall at floor level.
11c. Trobriand’s Body
The body of a frail man in dark robes lies atop a stone slab near the south wall. The man has long, wavy hair and a thick beard the color of iron, and he wears a metal ring on the index finger of his left hand.
Characters who have seen images of Trobriand know that the body lying on the slab is his. After Trobriand successfully transferred his spirit to an iron golem (see area area 13), his body was placed here by the scaladar servants that guard area area 11b. The body is in stasis but can be attacked normally. It is
Treasure
Trobriand wears a black metal ring on the index finger of his left hand that controls scaladar and overrides all other rings that have that property. It functions only within Undermountain (see the “Scaladar” entry in appendix A).
12. Gate to the Stone Bridge
Standing Gate. Two 15-foot-tall standing stones are positioned near the west wall of this 20-foot-high room.
Bas-Relief. Spanning the wall behind the standing stones is a bas-relief depicting an armored dwarf with a greataxe fighting a hill giant atop a long, flat bridge.
The bas-relief depicts Torhild Flametongue, king of the ancient dwarven kingdom of Besilmer, fighting a mortal enemy atop the Stone Bridge, a monument that spans the River Dessarin to this day. With a successful DC 20 Intelligence (
If a creature uses a finger or a staff to trace Halaster’s rune on the surface of either of the standing stones, a gate forms between them and lasts for 1 minute. A
13. The Metal Mage
This 20-foot-high room contains an iron golem that has a head shaped like a metal skull. It stands between three iron-plated stone pillars that hum with magical power. With the aid of these pillars, Trobriand recently transferred his spirit into the golem.
Trobriand is looking forward to testing his new body and attacks intruders on sight, showing no mercy.
Trobriand
While his spirit is bound within the golem, Trobriand has a challenge rating of 22 (41,000 XP) and the statistics of an iron golem, with these changes:
- Trobriand has an Intelligence of 20.
- He has the Spellcasting trait described below.
Spellcasting
Trobriand is an 18th-level spellcaster. His spellcasting ability is Intelligence (spell save DC 20, +12 to hit with spell attacks). He has the following wizard spells prepared:
- Cantrips (at will):
fire bolt ,mage hand ,prestidigitation - 1st level (4 slots):
detect magic ,magic missile ,shield - 2nd level (3 slots):
blur ,detect thoughts ,misty step ,shatter - 3rd level (3 slots):
counterspell ,dispel magic ,fireball ,haste - 4th level (3 slots):
blight ,greater invisibility - 5th level (3 slots):
animate objects ,Bigby’s hand ,scrying - 6th level (1 slot):
chain lightning ,globe of invulnerability - 7th level (1 slot):
finger of death ,forcecage - 8th level (1 slot):
incendiary cloud ,power word stun - 9th level (1 slot):
power word kill
Deactivating or destroying one or more of the pillars, destroying the golem, or forcing the golem out of the room causes Trobriand’s spirit to vacate the golem and attempt to reunite with his normal body, which is hidden in area area 11c. If the characters have not destroyed his body, Trobriand’s spirit returns to it immediately, and he awakens in area area 11c as an archmage with the same spell list as in his golem form and the same spell slots remaining as he had when he left his golem body. His primary goal thereafter is to destroy the characters for meddling in his affairs.
If the golem in this room has not been destroyed when Trobriand’s spirit leaves it, the golem becomes an ordinary iron golem under the Metal Mage’s command and attacks intruders on sight.
If the characters have already destroyed Trobriand’s body in area area 11c, and then they deactivate or destroy at least one of the pillars in this room, Trobriand’s spirit is forced to leave the golem but has nowhere to go, effectively killing him.
Iron-Plated Pillars
A
Each pillar is a Huge object with AC 17, a damage threshold of 10, 80 hit points, and immunity to poison and psychic damage.
14. Man with the Rabbit’s Head
A short, plump, rabbit-headed man wearing a dirty servant’s uniform cowers in the square marked X on map 23. “Rabbithead” is a commoner, with these changes:
- Rabbithead is unaligned and unarmed (0 XP).
- He has the head of a rabbit. He can’t speak and knows no languages.
This poor fellow is a rabbit transformed by Arcturia’s magic into a unique humanoid. The transformation is permanent and can’t be undone except with a
Rabbithead retreated here to escape Arcturia’s presence and latches onto the adventurers, hoping they’ll protect him from her wrath. Characters who succeed on a DC 12 Wisdom (
If Rabbithead is shown the yellow sapphires from area 8, he indicates through gestures and furtive glances that the missing ones are kept in area area 17.
15. Gate to Neverlight Grove
A pair of 15-foot-tall standing stones dominates this room, the ceiling of which rises 30 feet high. The stones are covered with moss and have clumps of colorful mushrooms growing on them.
If a creature uses a finger or a staff to trace Halaster’s rune on the surface of either of the standing stones, a gate forms between them and lasts for 1 minute. A
16. Broom Room
This room is empty except for a dusty wooden broom that leans against the far wall.
17. Arcturia’s Court
Characters who listen at the doors to this room hear harp music beyond. The room has a vaulted ceiling 20 feet high and contains the following:
Arcturia. Arcturia—a gaunt figure with blue scales, bone spurs on her forearms and elbows, gossamer wings, and a flowing gown—dances to music atop a stepped dais 5 feet higher than the rest of the room.
Butterfly Swarm. Next to Arcturia, a harmless swarm of yellow butterflies has assumed a vaguely humanoid shape and is playing an elegant harp (see “Treasure” below). The harp rests on a stout wooden table. The swarm is under Arcturia’s control and disperses when Arcturia isn’t around.
Dais Doors. Set into the back wall of the dais are two identical doors. The southeast door is trapped (see “area Southeast Door” below).
Furnishings. Arranged throughout the hall are four stuffed chairs, four padded footstools, two divans, and two large coffee tables. (These furnishings are twelve Mimic in disguise. Arcturia considers them her most trusted friends. If the lich comes under attack or takes umbrage with visitors, the mimics are quick to reveal their true forms and fight alongside her.)
Animal-Headed People. Standing between eight pillars are six humanoids that have the heads of beasts. Three wear servants' uniforms and carry feather dusters, and three wear heavy armor and carry swords.
Arcturia
Arcturia is a lich, with these changes:
-
In addition to her walking speed, Arcturia has a flying speed of 60 feet and can hover.
-
She can cast the
alter self spell at will and uses the following list of prepared spells: -
Cantrips (at will):
mage hand ,prestidigitation ,ray of frost -
1st level (4 slots):
detect magic ,magic missile ,shield ,thunderwave -
2nd level (3 slots):
detect thoughts ,enlarge/reduce ,Melf’s acid arrow ,mirror image -
3rd level (3 slots):
counterspell ,dispel magic ,fireball ,slow -
4th level (3 slots):
blight ,polymorph -
5th level (3 slots):
animate objects ,telekinesis -
6th level (1 slot):
disintegrate ,flesh to stone -
7th level (1 slot):
reverse gravity ,teleport -
8th level (1 slot):
feeblemind ,maze -
9th level (1 slot):
true polymorph
Unable to abide normalcy and consistency, Arcturia fixates on transforming herself, her surroundings, and other creatures. Her moods are ever-changing as well.
If the characters destroyed her phylactery on level 14, Arcturia knows what they did and attacks them at once. Otherwise, she has no grievance with the adventurers and is happy to let them go on their way, neither helping or hindering their efforts.
Animal-Headed Humanoids
Like Rabbithead in area area 14, these six creatures are animals transformed into humanoids by Arcturia’s magic. They have the following traits in common:
- They are unaligned.
- They can’t speak and know no languages.
The three humanoids wearing armor are Champion (see appendix A) with the heads of a dingo, an iguana, and a stork. If Arcturia becomes embroiled in a battle, two of them fight on her side. The one with the dingo head, who secretly despises Arcturia, sides with her enemies against her. Each guard carries a yellow sapphire (see “Treasure” below).
The three servants are unarmed Commoner with the heads of an aardvark, a moth, and a shrew. Whenever Arcturia snaps her fingers and points to a spot in the room, these servants begin dusting that location and don’t stop until she snaps her fingers again. They otherwise avoid combat.
Southeast Door
This door has a stone wall behind it, inscribed upon which is an elder rune (see “area Elder Runes"). Determine the rune randomly by drawing a card from the Elder Rune Deck (see appendix B). The rune targets the creature closest to the open door. It then vanishes until the door is closed, whereupon another elder rune appears in its place.
Treasure
The harp played by the butterfly swarm is an
The yellow sapphires carried by the animal-headed guards fit into the pillars in area area 8. Each gemstone is worth 1,000 gp.
18. Animated Hallway
This 250-foot-long, downward-sloping hallway has been set into permanent animated motion by Halaster’s magic. It twists and undulates continuously, making it tricky to negotiate. Any creature that enters the corridor or starts its turn there must succeed on a DC 15 Dexterity saving throw or take 5 (
19. Double Door Roulette
Double Doors. Seven sets of double doors, six of them at the end of short hallways, stand closed.
Scintillating Pillar. A pillar at the center of the 20-foot-high room has deep notches cut into it, which pulse with a shifting rainbow of light.
Behind most of the double doors are blank stone walls. Only the southern set of doors holds a path forward: pulling open these doors reveals area area 22 beyond. Creatures that pass through the doorway get no sense that they’re leaving Undermountain and entering Halaster’s extradimensional tower.
Whenever a double door in this area is opened—except the one to the south (see above)—the pillar emits colored rays from its myriad notches, duplicating the effect of a
20. Hidden Helm
A 10-foot-square, 1-foot-thick secret door conceals this room. Despite its size, the door swings open easily.
Beyond the secret door is a circular room with a 20-foot-high, domed ceiling. It has these features:
Spelljamming Helm. In the middle of the room is a gilded wooden throne with a cushioned seat and backrest covered in black velvet sewn with silver stars. This high-backed, 200-pound chair is the
helm of the Scavenger , which was stolen by Halaster from the ship of the same name (see area level 19, area 13).Sensors. Near the ceiling float four invisible scrying sensors created by the four Ultroloth in area 21a using
clairvoyance spells. If the ultroloths spot intruders in the room, they teleport to this location and attack.
Helm of the Scavenger
Wondrous item, legendary (requires attunement by a spellcaster)
This ornate chair is designed to propel and maneuver a ship through space.
Passive Properties
The following properties of the helm come into play even when no creature is attuned to it:
- When placed aboard a vessel weighing between 1 and 100 tons, the helm generates an envelope of fresh air around the ship while it is in the void of space (but not underwater). This envelope extends out from the edges of the hull in all directions for a distance equal in length to the vessel’s beam, so that creatures aboard and near the ship can breathe normally in space. The temperature within the air envelope is 70 degrees Fahrenheit.
- When placed aboard a vessel weighing between 1 and 100 tons, the helm generates an artificial gravity field while the ship is in the void of space, so that creatures can walk on the ship’s decks as they normally would. Creatures and objects that fall overboard bob in a gravity plane that extends out from the main deck for a distance equal in length to the vessel’s beam.
Active Properties
The sensation of being attuned to the helm is akin to being immersed in warm water. While attuned to the helm, you gain the following abilities while you sit in it:
- You can use the helm to propel the vessel across or through water and other liquids at a maximum speed in miles per hour equal to your highest-level unexpended spell slot.
- You can use the helm to propel the vessel through air or space at a maximum speed in miles per hour equal to your highest-level unexpended spell slot × 10.
- Provided you have at least one unexpended spell slot, you can steer the vessel, albeit in a somewhat clumsy fashion, in much the same way that oars or a rudder can maneuver a seafaring ship.
- Whenever you like, you can see what’s happening on and around the vessel as though you were standing in a location of your choice aboard it.
Drawback
While attuned to the helm, you cannot expend your own spell slots.
21. Displaced Vault
These chambers were built by Melairkyn dwarves on another level. Halaster moved them here.
21a. Acid and Glass
Ultroloths. Four Ultroloth (each marked with a U on map 23) lurk in alcoves along the north and south walls of this 30-foot-high room.
Glass-Covered Acid Pit. The floor is a 6-inch-thick sheet of transparent glass, below which is a 30-foot-deep pit containing a 20-foot-deep pool of yellow acid. Visible through the churning, translucent acid are three 1-foot-diameter pitted iron wheels affixed to the pit floor in a triangular formation.
Secret Door. A secret door in the east wall is locked.
The ultroloths spend most of their time using
Each 10-foot-square section of glass floor has AC 13, a damage threshold of 10, 25 hit points, and immunity to poison and psychic damage. Destroying three or more 10-foot-square sections causes the remainder of the glass floor to shatter, dropping all creatures standing on it into the acid. Any creature that enters the acid or starts its turn in it takes 33 (
A character can use an action to try to turn one of the iron wheels at the bottom of the acid pit, doing so with a successful DC 16 Strength (
The secret door is above the acid and held shut by three internal sliding bolt locks, each of which is attached to one of the submerged iron wheels in the acid pit. In lieu of turning those wheels, characters need three separate
21b. Nimoar’s Shield
This room appears empty except for dust and cobwebs. A thorough search reveals a stone peg protruding from the middle of the east wall at a height of 6 feet.
Treasure
If the word “xunderbrok” is spoken aloud anywhere in this room, a wooden shield materializes on the stone peg. Iron spikes protrude from the shield’s edges, and a cracked orc skull is painted in black on its outer surface. A
Nimoar’s shield is a
Halaster’s Tower
Encounters in Halaster’s tower (areas 22 through 36) are keyed to map 23. The tower is contained in a demiplane that exists outside Undermountain, yet all the normal restrictions to magic apply (see “area Alterations to Magic"). A portal connects area areas 23 and area 26, allowing passage to and from the tower.
Ceilings in the tower are 20 feet high and flat. All interior spaces are lit by
22. Tower Entrance
The double door to the north pushes open to reveal area area 19 beyond. Creatures that head north through the doorway get no sense that they’re leaving Halaster’s extradimensional tower and returning to Undermountain.
This room, which has several other doors leading away from it, contains the following features:
Statue. Standing atop a raised stone dais in the middle of the room, facing the double door, is a life-size statue of Halaster, his arms raised before him and his face bearing an awkward smile.
Rat. Gnawing on a piece of celery at the foot of the statue is an ordinary, harmless rat.
When he is not
23. Gnome with No Name
A 4-foot-tall, 2-foot-wide bronze-framed mirror leans against the far wall in this otherwise empty room. A creature that gazes into the mirror sees its reflection take the form of a female gnome in leather armor. She speaks Common and Gnomish, and is surprised to see the characters. Halaster trapped her in the mirror so long ago that she has lost track of time. The gnome has forgotten her name, after not interacting with other creatures for centuries. She longs to be free and asks the characters to help her.
The mirror is a Medium object with AC 11, 4 hit points, and immunity to poison and psychic damage. Breaking it or casting a successful
24. Potion Brewery
Cauldron. Fire erupts from a hole in the middle of the floor. Floating 1 foot above the fire is a hefty iron cauldron big enough for a person to hide in. A plume of black smoke rises from inside the cauldron.
Paraphernalia. Behind the cauldron rests a wooden table cluttered with brewing equipment. The floor around the table is strewn with shattered glass and empty flasks. Tucked under the table is a wooden crate with Halaster’s personal rune burned into its sides.
Demilich. Floating behind the table is a demilich that looks like a human skull with a jagged crack that extends above and below one eye socket.
Shelves and Ladder. The walls are lined with 10-foot-tall, wooden shelves packed with jars of pickled newts, frogs' eyes, and other common ingredients used in the brewing of potions. A wooden ladder on rollers is attached to a rail mounted above the shelves.
This demilich is all that remains of Branta Myntion, a wizard who fell in with a bad crowd. Her hunger for magic set her on an evil path as she hunted down and killed other wizards to acquire their spellbooks. Before old age could claim her, Branta transformed herself into a lich. In this form, she came to Undermountain to plunder its magic. Halaster captured and enslaved her, promising to free her if she helped him brew potions. Tragically, that promise went unfulfilled.
Deprived of the ability to feed souls into her phylactery, which lies hidden in a dungeon far from Waterdeep, Branta’s skeletal form deteriorated. Now, over a century later, only her skull remains. Years of captivity have driven the demilich insane, and it attacks anyone other than Halaster.
Although powerful wards prevent the demilich from leaving Halaster’s tower, the tower is not considered its lair. Consequently, the demilich doesn’t gain lair actions, nor does the tower exhibit the demilich’s lair traits.
Cauldron
The cauldron is held aloft by magic, and the fire beneath it is also magical. Casting
Elixir of Timelessness
The cauldron contains twenty doses of a hot, oily black elixir that has grains of sand floating in it. A creature that imbibes a single dose of the liquid gains the ability to cast
Crate
The crate contains thirty corked and labeled bottles of Halaster’s Futuristic Frogmash, a foul-tasting homebrewed wine. Each label bears Halaster’s rune and the date 1531 DR.
A
25. Factory
Unseen Servants. Six Living Unseen Servant (see appendix A) are gathered around two wooden tables, where they are using mortars and pestles to grind dead beetles into ink, and wooden frames and stone scrapers to stretch and scrape leather to create sheets of parchment. The servants ignore visitors.
Shelves. Standing against the walls are wooden shelves lined with jars of ink and rolled sheets of blank parchment.
26. Gate to Icewind Dale
The room contains a pair of 15-foot-tall standing stones. Carved into each stone are pictographs of primitive humans using spears to hunt reindeer and fend off yetis.
If a creature uses a finger or a staff to trace Halaster’s rune on the surface of either of the standing stones, a gate forms between them and lasts for 1 minute. A
27. Rantantar’s Wand
This room serves as a parlor where Halaster entertains guests (infrequent though they may be).
Furnishings. Ornate wooden chairs with padded seats and backrests line the walls. Between the chairs stand alabaster busts of Halaster atop wooden pedestals.
Wand. Lying on the floor in the middle of the room is a 20-foot-diameter, frayed circular rug adorned with Halaster’s personal rune. Floating 10 feet above the rug is a golden wand with spinning orbs of colored glass at one end (see “Treasure” below). It attacks any creature that enters the room unaccompanied by Halaster.
Treasure
Following the destruction of Rantantar, one of his oldest apprentices, Halaster recovered the dead archmage’s
The animated wand has the statistics of a animated object (tiny) (see the
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If the animated wand is grabbed while Rantantar’s spirit is lodged inside it, a contest of wills ensues. The creature grabbing the wand must immediately make a DC 20 Charisma saving throw. On a failed save, the creature is forced to release the wand. On a successful save, the wand becomes inanimate until the creature lets go of it. If a spellcaster holds the wand long enough to become attuned to it, that act banishes Rantantar’s evil spirit from the wand forever.
28. Hidden Treasure
Pentagram. A large pentagram is inscribed on the floor.
Statue. A life-size stone statue of Halaster wearing a blindfold stands in an alcove. The statue holds a stout staff that has a red dragon’s head at each end of it and is pointing the staff toward the pentagram.
Secret Door. A secret door in the northern alcove conceals a staircase that leads up to area area 32.
The pentagram and the space above it (a cylinder 20 feet high and 40 feet in diameter) are contained within a permanent antimagic field (see the
Shield of the Uven Rune
Wondrous item, very rare (requires attunement)
This shield is made from the scale of an ancient white dragon. It has a rune burned into its outward-facing side. A character who examines the rune and succeeds on a DC 20 Intelligence (
While holding the shield, you benefit from the following properties.
Winter’s Friend
You are immune to cold damage.
Deadly Rebuke
Immediately after a creature hits you with a melee attack, you can use your reaction to deal
Bane
You can cast the
Gift of Vengeance
You can transfer the shield’s magic to a nonmagical weapon by tracing the uven rune on the weapon with one finger. The transfer takes 8 hours of work that requires the two items to be within 5 feet of each other. At the end, the shield is destroyed, and the rune is etched or burned into the chosen weapon. This weapon becomes a rare magic item that requires attunement. It has the properties of a +1 weapon. The bonus increases to +3 when the weapon is used against one of the following creature types, chosen by you at the time of the magic weapon’s creation: aberrations, celestials, constructs, dragons, elementals, fey, fiends, giants, or undead.
Statue of Halaster
A character who examines the statue and succeeds on a DC 15 Wisdom (
When he is not
29. Apprentice Portraits
Seven tall, framed portraits hang on the walls of this room. Embedded in the wall beneath each portrait is a small bronze plaque bearing a name. A character who examines the portraits and plaques can, with a successful DC 20 Intelligence (
Each apprentice is shown wearing a
Rantantar is a fat, frowning man scarred by fire. He wears ornate purple robes and grasps what looks like a
Nester is a handsome, slender man with thinning hair and a penetrating stare. He wears a plain black robe and many rings on his steepled fingers. Tattooed on his forehead is a tiny black rune. A successful DC 10 Intelligence (
Trobriand the Metal Mage is a stoic, bearded man with black hair, black robes, and tinker’s goggles. Perched on his shoulder is a tiny iron scorpion.
Muiral the Misshapen is an ugly, powerfully built man with messy brown hair and a cruel sneer. He wears battered plate armor and has a steel helm with a scorpion motif tucked under his right arm. Clutched in his left hand is a longsword that drips blood.
Arcturia has straw-like hair, bony features, blue-tinged skin, and an exasperated expression. She wears a wide-brimmed conical hat and a robe of butterflies. She holds up a finger, above which floats a tiny, glowing sigil. A successful DC 10 Intelligence (
Marambra Nyghtsteel is a striking woman with long auburn hair and an empty, distant gaze. She wears a black robe and holds a staff topped with a rune. A successful DC 10 Intelligence (
Jhesiyra Kestellharp is a young, plain-looking woman dressed in yellow and blue robes. Her face betrays the subtlest hint of a smile. Her portrait has been slashed in half.
The first character who steps within 5 feet of the torn portrait of Jhesiyra Kestellharp hears a woman’s voice whisper in their head: “So close…” If the portrait is repaired using a
30. Scrying Room
Hanging on the wall are what appear to be realistic paintings of cityscapes in gilded wooden frames. In truth, these “paintings” are magical scrying sensors that are fixed on the following locations in Waterdeep:
- The city’s north gate, as seen from inside the city
- The city’s south gate, as seen from inside the city
- The Swordmaiden, one of the walking statues of Waterdeep, in the North Ward
- Heroes' Garden, a park in the Sea Ward
- The exterior of the House of Wonder (temple of Mystra) in the Sea Ward
- The exterior of the Font of Knowledge (temple of Oghma) in the Castle Ward
- The exterior of Ahghairon’s Tower in the Castle Ward
- The exterior of Blackstaff Tower in the Castle Ward
- The Market in the Castle Ward
- The interior of the Yawning Portal’s taproom and the entrance to Undermountain
Characters acquainted with Waterdeep can easily recognize the locations being scried upon, since they are all prominent landmarks. Breaking a scrying device’s frame or removing it from the wall destroys its magic.
31. Art Studio
Eight Living Unseen Servant (see appendix A) are painting four new portraits of Halaster and carving a statue of him in this room. Characters who enter the room see the following features:
Painters. Brushes held by invisible hands are dabbing paint onto rectangles of canvas propped up on four wooden easels. At the same time, floating hammers and chisels are nibbling away at a large block of stone.
Subject. Posing next to the stone block is a silent, illusory image of Halaster Blackcloak in a seductive pose.
The illusion of Halaster has no substance and changes its pose every minute. A successful
The unseen servants ignore visitors, but they attack if their work is interrupted or if the illusion of Halaster is dispelled.
32. Jhesiyra’s Warning
This room is furnished identically to area area 27 (except for the presence of Rantantar’s wand), perhaps causing characters to think they have reentered that room somehow.
As one or more characters cross this room and head toward the door to area area 33, Jhesiyra (see “area Jhesiyra Kestellharp") sends each of them the following telepathic warning in a language they know: “The Mad Mage waits for you beyond the next door. Prepare yourselves!”
33. Mad Mage Showdown
Halaster Blackcloak (see appendix A) awaits the characters in this room, which has the following features:
Raised Alcove. Steps ascend to a raised alcove that contains a purple marble throne surrounded by stacks of aged books. Carved into the wall behind the throne is Halaster’s personal rune, and beneath the rune is a locked iron chest. (Halaster sits in the throne and is
invisible when the characters enter.)Statue. On the opposite side of the room from the throne is a life-size stone statue of a nude Halaster wearing a cowboy hat and riding a donkey.
Magic Circle. Inscribed on the floor in the middle of the room is a 40-foot-diameter circle of glowing runes. Halaster uses it to summon an empyrean who owes him a favor. (The circle serves no other purpose.)
When he is seated in the throne, Halaster remains
Halaster orders Nalkara to slay the characters, regardless of his feelings toward them. If the characters pass the test by defeating the empyrean, Halaster again uses the throne to throw his voice and congratulates them. His next actions depend on his current goal (see “area Halaster’s Goals"):
- If the characters took any actions to further Halaster’s current goal, he greets them warmly, thanks them for their help, returns any magic items they sacrificed to reach this level (see area area 35 on level 22), and allows them to leave his tower by way of the standing gate in area area 36 (which he activates for them). The characters gain no XP for “defeating” Halaster in this fashion. If they refuse to leave, Halaster becomes annoyed and attacks them.
- If the characters took any actions to hinder Halaster’s current goal, the Mad Mage expresses his displeasure and attacks them.
Five minutes after Halaster dies, the demiplane containing his tower collapses, scattering its contents across the Astral Plane (see “area Conclusion").
Halaster’s Throne
The throne has the following magical properties:
- When seated in the throne, a creature can use a bonus action to turn
invisible or to end the effect. The invisibility ends automatically when the creature is no longer seated in the throne. - A creature that speaks while seated in the throne can choose to throw its voice, making it seem to originate from any point in the room that the creature can see.
Nalkara the Empyrean
Nalkara is the neutral evil daughter of Auril, the god of winter, and Thrym, the god of the frost giants. She looks like a strikingly beautiful frost giant with pale blue skin, cold blue eyes, and crackling blue flames for hair. When she is happy, everything around her seems bright and warm. When she’s unhappy, her surroundings become darker and colder.
Statue of Halaster Riding a Donkey
When he is not
Treasure
Hidden behind the stacks of books are any magic items the characters sacrificed to reach this level (see area area 35 on level 22).
Most of the books piled around the throne are worthless, rambling texts on the nature of magic and the multiverse. Among them are nine leather-bound spellbooks bearing Halaster’s personal rune. Collectively, these spellbooks contain every spell on the wizard’s spell list in the Player’s Handbook. Individually, each book holds the spells of a specific level, 1st through 9th. Add spells from other sources you see fit.
Hidden in the cut-out pages of a leather-bound novel titled Longsaddle Sunset is a revolver loaded with six bullets (see “Firearms” in chapter 9 of the Dungeon Master’s Guide).
The iron chest behind the throne has an
34. Flying Saucer
This room contains one of Halaster’s magical creations: a 20-foot-diameter flying saucer made of gleaming metal with its three landing struts extended. Surmounting the saucer is a hinged metal dome that is opaque from the outside and transparent from the inside. The entrance to the cockpit is 10 feet off the floor when the saucer is landed.
The saucer is a Huge object with AC 19, 200 hit points, a flying speed of 60 feet, the ability to hover, and immunity to poison and psychic damage. It is not airtight. Provided it has 50 or more hit points remaining, the saucer can be repaired as follows:
- Each casting of the
mending cantrip restores 1 hit point to the damaged saucer. - A character who has tinker’s tools, proficiency in the
Arcana skill, and 10 gp worth of replacement parts can spend 1 hour making repairs; at the end of the hour, the saucer regains1d4 hit points.
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The dome covers a cockpit that contains a padded leather seat and a slanted metal console. Embedded in the console is an ornate metal joystick (see “Treasure” below) and three metal buttons labeled “Hover,” “Land,” and “Teleport.” The rest of the saucer’s interior is taken up by arcane machinery.
Pressing the “Hover” button causes the landing gear to retract and the saucer to levitate 10 feet in the air. When the saucer is airborne, the joystick can be used to fly the saucer in any direction the pilot desires.
Pressing the “Land” button causes the landing gear to extend and the saucer to sink at a rate of 10 feet per round until it lands on a surface that can bear its 2-ton weight. The joystick locks in place and is immovable while the saucer is landed.
Pressing the “Teleport” button teleports the saucer and its pilot, along with anything the pilot is wearing or carrying, to a lonely hilltop in the Forlorn Hills east of Waterdeep. The ship can’t teleport again for 24 hours, and pressing the button again has no effect until this power recharges.
Treasure
The joystick that controls the flying saucer is a
35. Exercise Room
Golems. Two Flesh Golem are working out in this room. One golem is doing shoulder shrugs with two 100-pound iron kettlebells. The other switches back and forth between jumping jacks and shadowboxing.
Exercise Equipment. Padded leather mats are strewn upon the floor amid kettlebells and stacks of iron plates of various weights. Against the far wall rests a padded workout bench and an iron barbell bearing 400 pounds of weight. Behind the bench, hanging on the wall, is a set of boxing gloves.
If a character uses any of the room’s equipment, the nearest golem stops its workout and stands ready to assist. The golems attack only if damage causes them to go berserk.
If a character dons the boxing gloves, one golem moves to the middle of the room, raises its fists, and trades blows with anyone who tries to box with it. It takes no damage from an adversary’s gloved fists.
36. Gate to Triboar
This room contains a pair of 15-foot-tall standing stones. Lashed to each stone with 50 feet of hempen rope is an inanimate scarecrow, like the ones found in farmers' fields. Perched atop the northernmost standing stone is an ordinary crow (use the raven statistics). The crow caws at anyone who enters the room and bonds with a random character.
If a creature uses a finger or a staff to trace Halaster’s rune on the surface of either of the standing stones, a gate forms between them and lasts for 1 minute. A
Conclusion
If Halaster is killed, the demiplane around his tower (areas 22 through 36) collapses 5 minutes later without warning. As the tower is torn asunder, its contents are blasted into the far corners of the Astral Plane. Characters who are holding onto one another or are tethered together end up in the same place on the Astral Plane until they find a means of escape or until a githyanki-crewed astral warship stumbles upon them. See chapter 2 of the Dungeon Master’s Guide for more information on the Astral Plane and its perils.
Halaster’s death also deactivates all gates in Undermountain. These gates reactivate when the Mad Mage re-forms
During Halaster’s absence, Jhesiyra (see “area Jhesiyra Kestellharp") tries to seize control of Undermountain. Does she succeed? That’s up to you. If she is successful, Jhesiyra takes her place as the new master of the dungeon, and Halaster does not return. Whether Jhesiyra remains disembodied or assumes a corporeal form when she usurps Halaster’s control over Undermountain is also for you to decide, but one thing she won’t do is reactivate Halaster’s gates. She doesn’t trust them and would prefer to create her own gates in due time. If Arcturia and Trobriand are still around, Jhesiyra plots to destroy them before they turn against her, and she might even draft adventurers to help her.
Existing in a disembodied state for so long has done little to preserve Jhesiyra’s sanity, and it remains an open question whether Undermountain becomes a safer place with her in charge. In all likelihood, the dungeon will remain a perilous location, as Jhesiyra’s fear that Halaster might someday return prompts her to ward the dungeon against that eventuality.
If Jhesiyra is unable to seize control of Undermountain, she continues to lurk in the dungeon as a disembodied entity, waiting for another opportunity to emerge. Unaware of Jhesiyra’s attempt to dethrone him, Halaster re-forms in Undermountain as he has done many times before. He doesn’t take being killed personally, but it inspires him to toughen Undermountain’s defenses so that the next group of adventurers can’t thwart him so easily. Much of his time in the coming months is spent creating a new demiplane and a new tower to replace the ones that were destroyed after he died.