This chapter, intended for DMs, details a dungeon called the Donjon Sphere. You can use this dungeon to describe the fate of a character who draws the Donjon card from a Deck of Many Things. This chapter also includes suggestions for other ways adventurers might end up in the Donjon Sphere, as well as advice for how to continue a campaign or keep it on track if the party gets split up.
The Donjon Sphere
The Donjon Sphere is a metal sphere that drifts through the Astral Sea. Centuries ago, an unknown species of intelligent beings built the sphere to capture and contain specimens from across the cosmos. They used strange magic to peer into the minds of their captives and observe them in simulated environments, curious to understand the minds of these alien creatures. When the first Deck of Many Things was created, the Donjon card was linked to the sphere, sending prisoners there.
The collective distress of the sphere's prisoners ultimately attracted the attention of a group of feyrs: Astral Sea monsters that feed on creatures' nightmares. The feyrs infiltrated the Donjon Sphere and wrought havoc, forcing the sphere's stewards to abandon it. After devouring the nightmares of everyone left inside the sphere, the feyrs moved on.
Since then, the Donjon Sphere has drifted through the Astral Sea. Automated systems keep the vessel working and on course, and Constructs called detention drones bring in a steady supply of fresh specimens. However, swaths of the sphere have fallen into disrepair or outright mayhem. For new arrivals, many brought by a Deck of Many Things, the anarchy means it's never been easier to wriggle free of the dungeon's crumbling wards and traps. However, this same chaos still makes banishment to the sphere extremely perilous.
Finding the Sphere
The Donjon Sphere is too small to be observed from any planet's surface without a telescope or magical aid, but clues to the sphere's whereabouts can still be found among the stars.
A character with a Deck of Many Things can deduce the Donjon Sphere's location by spending 8 hours studying the night sky and using the cards as a divination tool. Afterward, the character must succeed on a DC 22 Intelligence (Arcana) check to determine the sphere's coordinates in the Astral Sea. On a failed check, the character fails to calculate the sphere's location but can try again the next day, reducing the DC of the check by 1 for each consecutive attempt. Other methods of finding the sphere are detailed in the "Adventure Hooks" section below.
Once the sphere is located in the Astral Sea, the characters must reach it, probably using teleportation magic or a spelljamming vessel.
Adventure Hooks
Certain powerful organizations know the Donjon Sphere's location:
Layers
The Donjon Sphere's hollow interior is divided into several nested layers, as shown in 16. A complex web of metal tunnels and gears, navigable only by the sphere's specially programmed detention drones, separates the layers.
Outer Surface
The outer surface of the sphere is perfectly smooth, made from hundreds of panels of rare space metals. When debris or attackers mar the surface, repair drones replace the damaged panels within hours. A 50-foot-wide circular hatch just off the sphere's equator is the only surface entrance. This hatch opens and closes automatically for detention drones leaving and entering the sphere.
The ends of a sharp spindle protrude from each of the sphere's poles like antennae. Each spindle siphons excess energy from the sphere's power core, creating an energy shield that obscures the structure from most divination magic and traditional means of observation.
Gilded Labyrinth
A three-dimensional maze of brassy metal separates the sphere's surface from its inner levels. This so-called Gilded Labyrinth delays escape. Few escapees last long in the maze before they're recaptured by the sphere's detention drones, which know every inch of the complex.
In addition, like the wrinkles of a brain, the Gilded Labyrinth's countless reflective surfaces and edges amplify the invisible energy radiated from the sphere's power core. This effect can't be perceived by most creatures, but the energy collected is vital to the sphere's continued operation.
Donjon Core
The penultimate layer of the Donjon Sphere is described in detail below.
Power Core
The center of the Donjon Sphere is a massive molten ball created by the planar portal in 16 of the Donjon Core. This ball of fire generates power used throughout the sphere.
Running the Sphere
As a DM, your first challenge is getting all the characters to the Donjon Sphere; your next challenge is getting them out.
Splitting the Party
One way to get sent to the Donjon Sphere is to draw the Donjon card from a Deck of Many Things. When this happens, only the character who drew the card is banished to the sphere. But splitting the party can be challenging for your table, since it's difficult to keep all players engaged when one or more characters aren't present for a scene. How can the DM make this work?
Here are some ideas for keeping the entire table engaged if the party splits up, whether you're using the sphere or some other adventure location:
More advice on this topic, and how to accommodate a player who suddenly can't play their usual character, can be found in 17.
Escaping the Sphere
The "16" section later in this chapter includes a variety of areas where prisoners could be found; in particular, a trapped character is likely to be found in one of the stasis pods (16) or, if they resisted the detention drones, one of the isolation chambers (16). Alternatively, the character might have escaped already and be found wandering in the sphere.
If it would better fit your group, a trapped character can mysteriously reappear after a few in-game hours or days, rejoining the party on their own. Those who return from the sphere in this way never remember how they escaped—nor do they return wholly unchanged. Use the following curse, the Mark of the Donjon, to represent the transformation of a character who escapes the Donjon Sphere under mysterious circumstances.
Mark of the Donjon
A character who inexplicably reappears after spending time in the Donjon Sphere gains a lingering curse called a Mark of the Donjon. Determine the character's mark by rolling on the Marks of the Donjon table. A Mark of the Donjon lasts until removed by a Remove Curse spell or similar magic.
| d6 | Curse |
|---|---|
| 1 | The character can't stop shivering. |
| 2 | The character's vision is limited to a 5-foot-wide line pointing in a single direction. |
| 3 | The character gets nauseous near windows or doorways. If the character moves through such a threshold, the character has disadvantage on saving throws for 1 minute. |
| 4 | The character is plagued by nightmares of metal constructs. |
| 5 | The character is disoriented by wide-open spaces and has no sense of direction outdoors. |
| 6 | While in sunlight, the character has disadvantage on attack rolls. |
Donjon Sphere Features
The Donjon Sphere has the following features.
Ceilings, Lighting, and Walls
Ceilings in the Donjon Sphere are 10 feet high. Magic panels in the ceiling radiate 2.
The walls, which contain most of the sphere's machinery, are covered in panels of smooth, invulnerable metal sheeting.
Detention Drones
As the Donjon Sphere drifts about the Astral Sea, its systems send mechanical scouts called detention drones to nearby worlds to acquire new captives. Detention drones are Constructs that follow their ancient programming mindlessly and unerringly.
A detention drone is hostile to creatures without key cards (see the "16" section) but indifferent to a creature with a key card and anyone accompanying them, unless attacked. Detention drones don't carry key cards and can't open locked doors, but they can travel through maintenance shafts (see the "16" section). After 2d4 days of service, a detention drone must spend 24 hours resting in a rewinding station (such as those in 16) before it can resume service.
Detention drones vary in size, strength, and shape, though most are shaped like some kind of mechanical animal or plant. You can use the game statistics for any Construct to represent a detention drone; see "16" below for suggestions. All detention drones have a flying speed of 30 feet, the ability to hover, and the following action option:
Drone Patrols
Small groups of detention drones patrol the Donjon Sphere looking for escapees or intruders. When the text indicates that a drone patrol can be encountered in a location, roll on the Drone Patrols table to determine the number and types of the drones in the patrol, or choose an encounter you like.
| d6 | Patrol Composition |
|---|---|
| 1–2 | 1d6 quadrones |
| 3 | 1d4 suits of animated armor |
| 4–5 | 2 helmed horrors |
| 6 | 1 shield guardian |
Doors and Key Cards
Doors in the Donjon Sphere are made of the same space metals as the outer surface. A magical sensor above each doorway detects movement within 10 feet, which causes the door to open until no more movement is detected.
Some doors are color coded and require a key card to open. A creature carrying the appropriate key card can open a locked door by standing within 10 feet of the door and uttering the command word "open" in Infernal. Doors that require key cards to unlock are color coded on map 17.2 and called out in the text. The color of the door indicates the type of key card necessary to unlock it. Key cards come in three colors:
Casting a Knock spell on a red door's lock suppresses the lock for 10 minutes, casting a Knock spell on a blue door's lock suppresses the lock for 1 minute, and casting a Knock spell on a yellow door's lock suppresses the lock until the start of the caster's next turn.
Secret Doors
A number of secret doors are hidden in the Donjon Core. A character who searches a wall where a secret door is located and succeeds on a DC 20 Wisdom (Perception) check finds minuscule bumps along the wall's surface. Pressing these bumps causes the door to slide open.
Language
The Donjon Sphere's creators spoke and wrote Infernal. All instructions, labels, and other visible text in the sphere are in this language. The doors respond only to Infernal. Creatures native to the sphere presume anyone communicating with them in a language other than Infernal is a trespasser, though drones overlook the offense if the offender has a key card or is accompanied by a creature that does.
Magic in the Sphere
No spell other than Wish can be used to leave the Donjon Sphere or transport a character from one part of it to another. Effects that banish creatures to other planes of existence don't work inside the sphere. A creature that attempts to cast a spell or use a magic item or artifact to teleport from the sphere hears a dull fizzing in its head as the effect fails. The exception to this rule is magic that allows transit to the Border Ethereal, such as the Etherealness spell. A creature that enters the Border Ethereal from the Donjon Sphere is returned to the sphere upon leaving that plane.
Magic that summons creatures or objects from other planes, or that allows contact with beings from other planes, functions normally inside the Donjon Sphere, as does magic that involves an extradimensional space. Any spells cast within such an extradimensional space are subject to the same restrictions as magic cast in the Donjon Sphere. While characters are in the sphere, those who receive spells from deities or otherworldly patrons continue to do so.
Maintenance Shafts
Rectangular shafts, labeled 16 on map 17.2, allow detention drones to move throughout the sphere. Each shaft is protected by an iron grate, which has AC 19, 15 hit points, and immunity to poison and psychic damage. A detention drone within 10 feet of a grate can use an action to transmit a signal that shifts the grate aside. A drone that enters an open shaft can travel to any other shaft entrance in the Donjon core in 1d4 minutes.
Any creature other than a detention drone that attempts to travel from one shaft entrance to another must make a DC 20 Wisdom (Survival) check. On a failed check, the creature gets lost in the shafts for 2d4 hours before reemerging at a random shaft entrance in the Donjon core.
Donjon Core Locations
Prisoners are kept in the Donjon core. The following locations are keyed to map 17.2. The area described in this map is spherical; hallways leading off one edge of the map connect to other hallways on the opposite side.
1: Intake Circle
At the center of this octagonal chamber's floor is a permanent teleportation circle etched in stone. Many newcomers to the sphere arrive via this circle, including creatures that draw the Donjon card from a Deck of Many Things. The teleportation circle can be used only to enter the sphere, not to leave it.
The door to the south has been punctured with a jagged hole big enough for Medium characters to squeeze through. Metallic rubble blocks the tunnel that leads north.
One round after the circle is activated, a drone patrol arrives from 16 to escort any new arrivals to the stasis pods in 16. Huge prisoners are taken to massive stasis pods in 16 instead. Prisoners who put up an especially strong resistance might be taken directly to an isolation chamber in 16.
2: Pool
A young aboleth named Th'kogga is contained in the 80-foot-deep pool of water here. Aware of the room's controls but unsure how they operate, Th'kogga attempts to charm any creature that comes within 30 feet of the pool, then urges that thrall to help it escape.
An invisible seal, like that created by the Wall of Force spell, covers the pool. A detention drone or a creature with a blue or yellow key card can use an action to flip the lever on the south wall to disable or reenable the seal. Buttons around the lever control the pool's salinity, temperature, and automatic cleaning systems. If these controls are tampered with, Th'kogga's pool becomes unlivable; if forced to remain there, the aboleth dies in 2d4 days.
3: Engineer's Quarters
The sphere's chief engineer used this chamber as an office, a workshop, and living quarters.
The metal drawers along the south wall contain books inscribed with complex diagrams and technical instructions written in Infernal. One thick tome, titled Elevator Manual, contains the glyph sequence to bypass the lock on the elevator in 16. Another manual, titled Control Gems, describes how the sphere's creators employed the slaad control gems in 16 to contain the power of the elemental portal in 16.
Treasure
Scattered among the equipment are a blue key card, a set of tinker's tools, and five star rose quartzes worth 50 gp each.
4: Stasis Controls
On the north wall of this room are three levers in the upright position. Each lever controls the power to three blocks of stasis pods in area 5, which the windows along the south wall of this room overlook.
5: Stasis Pods
The doors to this chamber are red.
Nine massive metal containers fill this sterile chamber. Each contains ten coffin-like, crystalline stasis pods, which slide in or out of their container. Each stasis pod contains an unconscious Humanoid prisoner in a state of magical suspended animation. Most of these prisoners are commoners, but if you want to introduce a particular NPC to help the party or serve as an antagonist, that individual could be trapped in one of these pods. A character who drew the Donjon card from a Deck of Many Things could also be trapped here.
A stasis pod can be unlatched only from the outside. Each stasis pod is big enough to hold a Large creature and has AC 11, 15 hit points, and immunity to poison and psychic damage. If a living creature is placed in a powered, closed stasis pod for 1 minute, the creature has the unconscious condition and is in stasis. While in stasis, the creature doesn't require air, food, or drink, and it doesn't age. If the creature is removed from the stasis pod or the stasis pod's power is shut off, the creature regains consciousness after 1 minute or once it takes damage.
The pods in the southwest corner were ruined when an umber hulk burst from its malfunctioning stasis pod. It smashed the pods around it in a rage, then burrowed through the wall, creating 16.
6: Maintenance Hall
The door at this hall's north end is red.
A locked yellow hatch in the floor in an alcove off this hallway covers a ladder that connects to 16 below. The hatch is a yellow door.
7: Drone Containment
This chamber houses inactive detention drones. Repair bays called rewinding stations line the walls. Each rewinding station, which can hold one detention drone at a time, is a Large object with AC 11, 40 hit points, and immunity to poison and psychic damage.
Once per day, a drone patrol whose service time is almost expired comes here for rewinding. If engaged in combat, these drones have the unconscious condition after 1d4 + 1 rounds.
8: Prototype Lab
Metal plates, chains, cogs, and pipes are strewn about the oversized bays in this chamber. Each bay contains a prototype detention drone in a different state of assembly.
Only one prototype drone is functional, though it is inactive. A character with tinker's tools can spend 10 minutes repairing the drone and make a DC 15 Intelligence (Investigation) check. On a successful check, the drone's gears start winding, and it jerks to life. The drone, which calls itself Prototype WX-401 and resembles a human-size pitcher plant (use the tridrone stat block), is friendly toward the character who repaired it and follows that character's instructions to the best of its ability. It lacks the Detention Orb action of other detention drones.
9: Maintenance Shaft
These access tunnels are used by detention drones to move throughout the sphere. See "16" for more information.
10: Umber Hulk Tunnel
An umber hulk created this tunnel after freeing itself from a malfunctioning stasis pod in 16. Protruding bits of metal and low ceilings make the tunnel 8. To the south, the tunnel slopes upward to the Gilded Labyrinth.
11: Archive Antechamber
The fine chairs, desks, and shelves that once furnished this spacious antechamber have all been torn to shreds. A character who searches for tracks and succeeds on a DC 10 Wisdom (Survival) check finds large scrapes along the walls from the umber hulk that escaped 16. The door in this chamber's north wall is red.
12: Archive
Shelves full of massive logbooks line the walls of this two-story archive. A spiral staircase in the room's center connects to the archive's upper level. The books contain records on all prisoners inducted into the facility before the sphere's stewards fled.
The archive is occupied by Ganakki, a green slaad that appears as a pallid halfling scholar. Ganakki yearns to transform into a gray slaad and believes it can find the key to its metamorphosis somewhere in the Donjon Sphere. The party can learn much about the sphere from the slaad—including, possibly, a means of escape. However, Ganakki won't leave the archive. Ganakki has a red key card.
13: Ruined Trap Room
A closed portcullis divides this area from 16. The lever in 16 can raise the iron bars.
This hall was once a trap room featuring a balance beam that spanned a pit of grinding gears (see the 3 in 3). When a spelljamming ship from 16 crashed into the eastern side of the hall, the trap was destroyed. The nonfunctional gears are 8.
A secret door is concealed in the northeast corner of this room.
14: Crash Site
Rubble and metal wreckage cover the ground of this ragged fissure. The ceiling is 20 feet high, and its magical light panels have been destroyed, leaving this area in darkness.
When escaped prisoners tried to fly the damselfly ship in 16 to safety, they crashed it midway through the launch bay, causing a chain of explosions that destroyed this area. A thick wall of debris, not shown on the map, blocks off the western half of the crash site.
14a: Damselfly Wreckage
Pieces of a destroyed spelljamming ship lie scattered about the crash site. About 50 pounds of useful salvage (worth 500 gp) can be collected here.
14b: Survivor Camp
Two Solar Bastion knights (see 9) set up camp here after losing a companion to a large drone patrol. These knights came to explore the Donjon Sphere and its connection to the Deck of Many Things. The knights are as follows:
The knights are initially indifferent to the characters. If made friendly, they are willing to work with the party to escape the sphere. Emerist and Hielyo can tell the party about the secret doors between 16 and 16, though the knights don't know how to operate the elevator in area 19. They also offer the party a Spell Scroll of Comprehend Languages and a Chime of Opening with 4 charges remaining. The Chime of Opening can be used to open key card–locked doors like the Knock spell, as described in the "16" section; when used this way, one use of the chime is equivalent to one casting of the Knock spell.
14c: Labyrinth Entrance
This rough tunnel connects to the Gilded Labyrinth above.
15: Metallurgy Lab
The doors leading into the northeast and southwest ends of this chamber are both red.
Alien minerals and samples of rare ores line the shelves of this metallurgist's laboratory. An advanced detention drone (use the shield guardian stat block) stands in the room's corner. This Construct doesn't have a control amulet and can't be controlled like other shield guardians; it attacks any creature that enters the room without displaying a key card. It has the Confusion spell stored.
A secret door in an alcove in this room's northeast corner leads to 16.
Treasure
A set of smith's tools can be assembled from the lab equipment. On the shelves is a total of 30 pounds of rare space metals (worth 300 gp) and a fully charged Cube of Force.
16: Observation Room
This room is reached by ascending stairs. The window in this chamber overlooks the trap room below. A lever on the south wall controls the portcullis north of 16.
17: Trash Disposal
The eastern door to this chamber is blue.
Wide chutes along the edges of this room's floor connect to the crusher (16), allowing for easy disposal of waste materials.
A flumph named Bimbi hovers uncertainly, steeling itself to go down a chute to the crusher. It clutches a blue key card in its tentacles. Upon seeing the characters, Bimbi sighs with relief and explains it's searching for fresh brains to feed its friend, a mind flayer imprisoned in an isolation chamber (16). "I used to find brains in the brain room," Bimbi burbles. "But I knocked over some jars there, and the brains came to life!" If the characters agree to clear the "brain monsters" out of 16, the flumph gives them its key card.
18: Massive Stasis Pods
These large halls provide access to stasis pods built into the walls, each one larger and stronger than the ones in area 5. Each can hold a Huge creature and has AC 12, 50 hit points, and immunity to poison and psychic damage. Closed pods can be opened with a blue or yellow key card.
18a: Western Pods
This room's western door has been destroyed. The corpse of an unarmed frost giant lies in a heap next to a smashed stasis pod. A character who succeeds on a DC 10 Wisdom (Survival) check finds deep claw marks in the walls leading to area 18b, just like those in 16.
A blue door is in the northeast corner.
18b: Central Pods
A half-eaten chuul corpse lies near a broken stasis pod in this room. Claw marks mar the walls toward area 18c.
18c: Southern Pods
Two monstrous corpses lie on the floor of this room: an especially large owlbear and the umber hulk that broke the pods and killed the frost giant, chuul, and owlbear in the other rooms. After breaking a second pod in this room, the umber hulk met its match. The umber hulk's slayer, a remorhaz with 113 hit points remaining, stands in the center of this room, gathering its wits after its long stasis. When it sees the party, it attacks viciously, assuming the characters to be its imprisoners. The remorhaz relentlessly chases its opponents throughout the sphere.
19: Elevator Room
The northern door to this chamber is yellow.
The round platform in the center of this room is a mechanical elevator, which connects to 16 above and 16 below. A character who succeeds on a DC 20 Wisdom (Perception) check spots a panel on the east wall that, when pushed, reveals a secret door.
A lever on the wall controls the elevator's operation. On the wall to the lever's right is a card slot. On the lever's opposite side protrudes a circular mechanism with three interlocking dials, each with a set of alien glyphs around the circumference. The lever won't budge unless a yellow key card is inserted into the card slot or the three dials are set to the correct sequence of glyphs. The sequence can be found in the tome Elevator Manual in 16.
Once the elevator is activated, it takes 2 rounds for the elevator doors to close and 1 minute to reach area 16 or 16. After 5 minutes in either area, the elevator returns to this room.
A secret door is hidden in the eastern wall.
20: Isolation Chambers
Each of these metal chambers has a blue door. A slot for food delivery near the base of each door can be opened from the hall without a key card.
20a: Dead Naga
The desiccated remains of a spirit naga lie in this chamber. If the remains are disturbed, they rise as a bone naga and attack.
20b: Q'zar'ktan
The mind flayer in this room, named Q'zar'ktan, recently established a symbiotic relationship with Bimbi, the flumph in 16. Bimbi brings Q'zar'ktan preserved brains to eat. In exchange, Q'zar'ktan allows the flumph to harmlessly siphon some of the mind flayer's mental energy. Q'zar'ktan, morose and resigned to its fate in this dungeon, is initially indifferent to characters. It tells them about its predicament and mentions that the flumph hasn't stopped by in a while.
20c–e: Empty Chambers
These chambers are empty.
20f: Myconids
A myconid adult named Cluzong and two myconid sprouts have sprung up from the corpse of a svirfneblin prisoner in the corner of this damp cell. Having known nothing else, the myconids regard this cell as their home and have no desire to leave. They are indifferent to visitors.
21: Brain Chamber
The door to this chamber is red.
A strange, silver machine rests between a pair of metal chairs in the center of this room. Shelves lining the walls hold potion bottles and glass jars, many of which contain brains suspended in colorful liquid. Glassware on one shelf has been knocked over, covering the floor in broken glass.
Bimbi the flumph (16) accidentally spilled many of the jars here; the resulting alchemical stew mutated three of the brains in this room. The now-floating brains (use the grell stat block) attack any creatures that enter the area.
Two helmet-like contraptions, one per chair, dangle from silver cords attached to the machine in this room's center. When the machine is activated as an action while two creatures wear the helmets, the creatures instantly switch bodies (an unwilling creature can make a DC 18 Wisdom saving throw, causing the machine to fail on a successful saving throw). Each creature retains its personality and memories but exchanges all game statistics (its stat block or character sheet) with the other creature. Both creatures have the stunned condition for 1 minute as they adjust to their new bodies.
Treasure
Among the bottles and jars on the shelves are a Potion of Greater Healing and a Potion of Vitality.
22: Workers' Chambers
These sparse living quarters contain desks, beds, and shelves. Red doors connect 16, 16, and 16 to area 22a and the hallway to the west.
22a: Communal Room
A long metal table fills the center of this meeting room. Skeletal remains of three escaped prisoners are slumped on the table. The remains rise as three skeletons that attack anyone who enters the room.
A secret door is hidden in the northeast corner.
22b: Oily Floor
Spilled, flammable oil makes a 10-foot square of this room's floor 8.
22c: Glowing Orb
A glass orb wrapped in tattered oilcloth lies in one corner of this room. When uncovered, the orb shines light as if affected by the Continual Flame spell.
22d: Prisoner's Remains
Skeletal remains of an escaped prisoner lie in a corner of this chamber. Among the prisoner's gear are a suit of leather armor, a morningstar, a red key card, and a journal. The journal describes how the prisoner escaped 16 via a secret door and found some equipment in 16 before coming here.
22e: Head Steward's Office
A stone golem stands in one corner of this room. Still loyal to the steward who acquired it before the sphere's abandonment, the golem attacks any creature that enters the room.
The top drawer of the desk in this room contains a yellow key card.
23: Damselfly Bay
The door to this chamber is yellow.
A dragonfly-shaped spacecraft called a damselfly ship was once docked here. Some prisoners attempted to use the ship to leave the Donjon Sphere, but they crashed during the launch. The wreckage of the damselfly ship is scattered about 16.
24: Escape Pod
Three metal platforms in this bay once held escape pods, only one of which remains; it resembles a large coffin made of semitranslucent orange crystal.
One Medium creature or two Small creatures can fit inside the escape pod. If the pod's door is closed, a creature inside the pod can use an action to pull a lever, causing the stanchions holding the pod in place to collapse, a hatch in the ceiling to open, and a pulse of energy to propel the pod through a narrow tunnel and out of the Donjon Sphere, leaving the pod adrift in the Astral Sea. The entire sequence takes 3 rounds after the lever is pulled.
25: Simulation Chambers
The sphere's creators used these rooms to create simulations of the natural environments of prisoners. Normally large and empty, the rooms can be filled with whatever illusions the experimenter in 16 chooses. Windows look down on the two chambers from area 26, but those windows aren't visible from the simulation chambers. The two chambers are connected by a corridor that extends under area 26. The doors to this connecting corridor are blue.
25a: Western Simulator
This simulation chamber contains four mimics trained to play along with whatever illusion magic is cast on the room from 16. As long as the mimics have a scene to take part in, they cooperate peacefully, taking on the roles of whatever furniture, fixtures, or other domestic trappings best suit the illusion. If the room isn't affected by an illusion, the mimics assume the forms of two metal chairs, a table, and a bed.
25b: Eastern Simulator
Two lawful evil doppelgangers occupy this room. The doppelgangers take on a variety of disguises to match whatever illusion magic is cast on the room from area 26. If the room isn't affected by an illusion, the doppelgangers assume the forms of nondescript Humanoids cloaked in silvery robes.
26: Observation Room
Wide windows along the east and west walls of this elevated room overlook the adjacent simulation chambers; the windows aren't visible from the chambers below. A chaotic evil riffler (see 20) named Turner is in the room, trying to figure out the controls; Turner has a blue key card.
Simulation Controls
Beneath each window is a magical console that resembles a wide desk with a slanted top. Each console has AC 14, 25 hit points, and immunity to poison and psychic damage.
A creature with a blue or yellow key card can use an action at the console to activate one of the following spells, targeting the simulation chamber to which the console is closest. The spell's area is restricted to the dimensions of the simulation chamber in which it is cast. Each spell can be cast once per simulation chamber per day:
- Create Food and Water
- Major Image
- Mirage Arcane
- Sleep (cast as a 4th-level spell)
27: Observatory
An alcove at one edge of this chamber holds a platform for the elevator to 16.
A massive telescope protrudes from the center of this room, its lens aimed through a hole in the ceiling that extends all the way through the Donjon Sphere. A complex array of levers that lines the telescope can rotate the Donjon Sphere to allow the telescope to change its field of view. This telescope is a Telescopic Transporter (see 12). One or more characters could use it to escape the Donjon Sphere.
28: Crusher
Waste from 16 above arrives here to be pulverized by sloped grinding gears. Sufficiently ground-up materials fall through a screen to a conveyor belt that transfers them to the forge in 16.
A creature that enters a space of crushing gears for the first time on a turn or starts its turn there takes 27 (5d10) bludgeoning damage.
29: Forge
Crushed waste and scrap metal are transferred to this forge to be melted down and poured into molds. Two fire elementals tend the forge. They're friendly to anyone with a yellow key card, indifferent to those with a blue or red key card, and hostile to anyone without a key card.
The vat of molten metal here is 20 feet deep. A creature that enters the vat for the first time on a turn or starts its turn there takes 27 (5d10) fire damage.
30: Shuffler
A drone patrol monitors this area at all times.
Conveyors transport glowing-hot metal plates from the forge to this large sorting area, where machinery rotates, flips, and folds them into smaller forms before they're sent on to area 31.
The machinery forms a shifting maze of hazards. Any creature other than a detention drone that ends its turn anywhere in this area must make a DC 14 Dexterity saving throw. On a failed save, the creature takes 11 (2d10) bludgeoning damage plus 5 (1d10) fire damage, is lifted above the conveyor by the machinery, and has the grappled condition (escape DC 13).
31: Reconstructory
The Donjon Sphere constantly repairs itself. New metal plates, iron bars, and other construction materials are fabricated in this automated factory. Finished materials are removed from here into the maintenance shaft network, where they're handled by detention drones.
A creature that ends its turn in this area must make a DC 15 Dexterity saving throw. Small and smaller creatures have advantage on this save. On a failed save, the creature takes 22 (4d10) slashing damage as automation moves it through the maintenance shaft network; the creature ends its turn inside a random maintenance shaft somewhere on 16 (DM's discretion).
32: Control Gems
At each corner of this rectangular set of corridors is a circular room that contains a slaad control gem mounted in a filigreed contraption atop a metal pedestal. The gems control the planar portal in 16, which in turn generates the Donjon Sphere's fiery power core. Opening off one of the corridors is a circular chamber that holds a platform for the elevator in 16.
As an action, a character with thieves' tools can try to remove a control gem, doing so with a successful DC 17 Dexterity (Sleight of Hand) check. Alternatively, a character can remove a gem by force, taking an action and making a DC 15 Strength (Athletics) check. On a failed check, the pedestal unleashes an arc of lightning that deals 14 (4d6) lightning damage to the character who attempted to remove the gem.
For each control gem removed, the portal in area 33 becomes less stable, which in turn affects the sphere's power core. The lights throughout the facility start blinking, and the sphere fills with the sounds of hissing steam and groaning metal. These effects intensify with each control gem removed.
If two gems are removed, the power core at the heart of the Donjon Sphere implodes after 2d8 hours. This is reduced to 1d4 hours if three gems are removed, and to just 1d4 minutes if all four gems are removed. Replacing all four gems before the power core implodes resets the time limit.
If the power core implodes, the planar portal in area 33 expands to the size of the Donjon Sphere. The prison and all its contents are transported to the Elemental Plane of Fire, then the portal collapses on itself and disappears.
33: Portal Chamber
The massive metal doors to this room are yellow.
A portal to the Elemental Plane of Fire floats in this room, reduced to a fiery orb six inches in diameter by the control gems in area 32. The portal floats between two black, triangular pillars that channel energy from the portal to the power core at the heart of the sphere.
Planar Portal
The portal in the center of this chamber is surrounded by a powerful energy field. A creature that comes within 15 feet of the portal for the first time on a turn must make a DC 20 Constitution saving throw, taking 55 (10d10) force damage on a failed saving throw, or half as much damage on a successful one.
Additionally, a creature that fails this saving throw or touches the portal is caught in its energy field. The creature is ejected from one of the sphere's poles (50 percent chance of either) at a speed of 1 mile per round; once free of the sphere, the creature can move normally using the rules for movement in the Astral Sea.