At the center of the multiverse floats Sigil, the City of Doors — a torus-shaped city perched atop an infinitely tall spire, ruled by the enigmatic Lady of Pain and divided among fifteen philosophical factions who believe their ideology shapes reality itself. When an ancient artifact threatens to prove one faction's philosophy absolutely right, the city erupts into open war, and the adventurers must navigate treacherous alliances, planar portals, and fundamental questions about the nature of belief and power.
Story Arcs
Welcome to the Cage
The adventurers arrive in Sigil — called "the Cage" by locals — through one of its countless portals. They must quickly learn the rules of the city: the factions control everything, portals are everywhere but require specific keys, and the Lady of Pain kills anyone who worships her or threatens the city. The party is drawn into the faction politics when they witness a murder tied to a stolen artifact — a golden astrolabe that allegedly maps every portal in Sigil, granting its possessor unimaginable power.
The Faction Intrigues
Each major faction wants the astrolabe for its own philosophical reasons. The Harmonium wants it to impose order across the planes. The Xaositects want to shatter it and let chaos reign. The Mercykillers want it to hunt criminals across every reality. The adventurers are courted, threatened, and manipulated by faction agents as they investigate the artifact's location. Their search takes them through portals to the Outer Planes — from the lawful perfection of Mechanus to the howling chaos of Limbo — gathering clues and making enemies.
The War Erupts
The fragile peace between factions shatters when the astrolabe's location is revealed: it rests in the Armory, a heavily fortified structure in the Lady's Ward. Multiple factions launch simultaneous assaults to claim it, turning Sigil into a battlefield. Portals malfunction, dabus (the Lady's enigmatic servants) patrol with unusual aggression, and the Lady of Pain herself appears to be destabilizing. The adventurers must decide which faction — if any — should possess the astrolabe, or whether the artifact should be destroyed entirely.
The Lady's Judgment
As the Faction War reaches its climax, the Lady of Pain makes her displeasure known. She begins mazing faction leaders — trapping them in personal pocket dimensions with no escape. The astrolabe, when activated, reveals a terrible truth: belief literally shapes the planes, and if any single philosophy achieves total dominance, it would collapse the entire multiverse into a single, uniform reality. The adventurers must use this knowledge to broker peace, destroy the artifact, and restore the balance of belief that keeps the multiverse alive — all while avoiding the Lady's blades.
Session Outlines
These outlines are for planning reference only. Actual sessions are not created by the template.
Through the Portal
The party tumbles through an unexpected portal and arrives in the Hive Ward, Sigil's most dangerous slum. Introduce the alien geometry of the city — buildings curve upward in every direction, and the "sky" is more city overhead. A tout (guide) named Kylie approaches and offers to show them the ropes for a fee. She explains factions, portals, and the Lady of Pain. That evening, the party witnesses a murder outside the Smoldering Corpse Bar: a sage is killed by a shadowy figure who steals a golden astrolabe from his body. A Harmonium patrol arrives and suspects the party.
The Factions Take Notice
The murder investigation draws faction attention. A Mercykiller justiciar interrogates the party, an Athar priest offers to help in exchange for favors, and a Xaositect babbles cryptic clues that turn out to be genuinely useful. The murdered sage was a member of the Fraternity of Order — the Guvners — and the astrolabe was their prized research subject. The Guvners hire the party to recover it. Introduce the concept of portal keys and have the party use their first portal — stepping through a doorway while holding a specific flower — to travel across Sigil instantly.
The Harmonium Gambit
The Harmonium — Sigil's self-appointed police force — wants the astrolabe to map and control all portals, effectively locking down Sigil. Measure Three Torvus invites the party to the City Barracks to "assist the investigation," but it's really a recruitment pitch. If the party refuses, they find themselves harassed by Harmonium patrols. A secret meeting with a Harmonium defector reveals that Torvus is acting independently — the faction leadership doesn't know about the astrolabe yet, and Torvus plans to use it for a coup within the faction.
Into Mechanus
A clue points to Mechanus, the plane of absolute law, where the Guvners maintain a research library. The party travels through a portal (key: a perfectly balanced scale) to the clockwork plane. Enormous gears rotate beneath a sky of mathematical equations. The Guvner library is tended by modrons — geometric beings who speak in precise logical statements. The records reveal the astrolabe was forged by the ancient rilmani (planar balance-keepers) and has the power to prove or disprove any philosophical position — potentially rewriting reality itself. A rogue modron tries to steal the records.
The Chaos of Limbo
Following leads on the astrolabe thief, the party travels to Limbo — a churning maelstrom of elemental chaos where thought shapes reality. The Xaositects maintain a shifting stronghold here, and their factol (leader) claims to know who has the astrolabe. Navigating Limbo requires constant mental effort to maintain solid ground. A red slaad attack tests the party's ability to fight in a constantly shifting environment. The Xaositect factol reveals the thief is a Mercykiller agent who plans to use the astrolabe to track every criminal across every plane.
Mercykiller Justice
The party tracks the Mercykiller agent to the Prison, the faction's grim headquarters in Sigil's Lady's Ward. The Mercykillers are incorruptible in their pursuit of justice — but their definition of justice is absolute and merciless. The agent has hidden the astrolabe somewhere in the prison's labyrinthine depths. The party must infiltrate the Prison, either by stealth, deception, or cutting a deal with the faction. Inside, they encounter prisoners from across the planes and discover the Mercykillers have been using the astrolabe to peer into other realities, compiling a list of "fugitives from justice" across the entire multiverse.
The Astrolabe Revealed
The party recovers the astrolabe — or at least discovers its exact location. It has been moved to the Armory in the Lady's Ward, a neutral ground guarded by mercenaries. Word leaks to all the factions simultaneously. Tensions skyrocket as faction leaders mobilize. An emergency meeting at the Hall of Speakers in the Clerk's Ward devolves into accusations and threats. The Harmonium, Mercykillers, Xaositects, Athar, and Doomguard all claim the right to the artifact. The Guvners demand it be studied objectively. War is clearly imminent.
The Streets Run Red
The Faction War begins. Harmonium troops clash with Xaositect mobs in the Market Ward. Mercykiller squads raid faction headquarters. The Doomguard — who believe in entropy — assault the Armory not to take the astrolabe but to destroy it. Portals across Sigil flicker and malfunction. The party must navigate a city turned battlefield, choosing when to fight, when to run, and when to negotiate. Dabus float through the carnage, repairing damage to the city with their rebus-speech, but they are more aggressive toward faction combatants than usual.
The Lady Mazes
The Lady of Pain begins mazing faction leaders — each one vanishes into a personal extradimensional labyrinth with no exit. Factol after factol disappears. Panic grips Sigil. The party may witness a mazing firsthand: the Lady's shadow falls across a faction leader, her bladed headdress gleaming, and the leader simply ceases to exist on this plane. The message is clear — the factions are threatening Sigil's existence, and the Lady will not tolerate it. A desperate Guvner contact gives the party the key to enter the Armory before the Lady seals it permanently.
The Armory
The party breaches the Armory, fighting through faction agents who arrived first. Inside is a fortress filled with weapons and artifacts from across the planes. The astrolabe rests on a central pedestal, humming with power. When activated, it projects a map of every portal in Sigil — and more. It shows the belief-lines that connect the planes, the philosophical currents that literally hold reality together. A pit fiend leading a Baatezu strike team crashes through a portal into the Armory, seeking the astrolabe for the Blood War.
The Truth of Belief
With the astrolabe activated, the party sees the terrifying truth: every plane exists because beings believe in it. The Outer Planes are literally shaped by mortal belief. If the astrolabe is used to prove one philosophy absolutely correct, all competing beliefs would collapse, and every plane shaped by those beliefs would cease to exist — billions of souls unmade. The party must defend the astrolabe from faction zealots who refuse to accept this truth, including a Harmonium army that has breached the Armory's outer walls. A balor demon has joined the chaos, trying to steal the astrolabe for the Abyss.
The Balance Restored
The climactic session. The party must destroy the astrolabe before any faction claims it. Destroying it requires a specific ritual that the Guvner records described — it must be shattered simultaneously on four different planes, its fragments scattered where no single belief can reassemble them. The party splits the astrolabe into four pieces and uses Sigil's portals to distribute them to Mechanus, Limbo, Mount Celestia, and the Abyss — the four philosophical extremes. The act restores balance, the Lady of Pain releases the mazed faction leaders (chastened and diminished), and Sigil's portals stabilize. The Faction War ends not with victory but with the realization that no single truth can — or should — dominate.
NPCs
Kylie the Tout
Tiefling · Street Guide
A sharp-tongued, resourceful tiefling who makes her living guiding newcomers (called "Clueless") through Sigil's bewildering streets. She knows every shortcut, portal, and back-alley deal in the Cage. Underneath her mercenary exterior, she genuinely cares about Sigil and its people, and she serves as the party's anchor in a confusing multiverse. She peppers her speech with Sigil slang — "berk," "addle-cove," "the dark of it."
Measure Three Torvus
Human · Harmonium Officer
An ambitious Harmonium officer who believes absolute order is the only path to lasting peace. He is rigid, humorless, and utterly convinced of his own righteousness. He pursues the astrolabe not for the faction but for himself, planning to use it to impose Harmonium law across every plane. His fanaticism masks a deep insecurity — he secretly doubts the Harmonium's methods but cannot admit weakness.
Factol Pentar
Human · Doomguard Factol
The leader of the Doomguard, a faction that believes entropy is the natural and proper end of all things. Pentar is surprisingly calm and philosophical for someone who advocates universal destruction. She sees the astrolabe as an abomination — an attempt to impose permanent structure on a multiverse that is meant to wind down. She would rather destroy it than let anyone use it, and she commands an arsenal of entropy-touched weapons.
Rule-of-Three
Cambion · Information Broker
A mysterious cambion who always speaks in groups of three statements. He operates from a crumbling tower in the Lower Ward, trading in secrets and favors. He knows more about the astrolabe than he lets on — he was present when the rilmani forged it millennia ago. His motives are inscrutable, but he seems to favor balance over any single faction's victory. Every piece of information he gives is technically true but carefully incomplete.
Alluvius Ruskin
Tiefling · Apothecary and Athar Sympathizer
A mild-mannered apothecary in the Lower Ward who sells remedies brewed from planar ingredients. She is secretly an agent of the Athar — the faction that denies the gods are truly divine. She wants the astrolabe to prove the gods are merely powerful beings, not worthy of worship. She is kind, soft-spoken, and will betray the party without hesitation if it serves the Athar's goals.
Fell
Dabus · Tattoo Artist
A unique dabus — the Lady of Pain's enigmatic servants — who was cast out for reasons unknown. He runs a tattoo shop in the Hive Ward, communicating through rebuses (picture-puzzles that float in the air). His tattoos are magical and can serve as portal keys or protective wards. He knows more about the Lady's intentions than any mortal, and his tattoos sometimes contain prophetic imagery that only becomes clear later.
Shemeshka the Marauder
Arcanaloth · Crime Lord
A jackal-headed arcanaloth who is one of Sigil's most powerful crime lords, operating from a luxurious den in the Lady's Ward. She deals in information, favors, and contracts — always with hidden clauses. She views the Faction War as a business opportunity and will sell information to all sides simultaneously. She is utterly amoral, devastatingly intelligent, and always three steps ahead of everyone else in the room.
Locations
The Hive Ward
Sigil's most desperate neighborhood — a sprawl of crumbling tenements, refuse-choked alleys, and desperate souls from a hundred planes. Cranium rats swarm the gutters, and the Dustmen (faction of the dead) collect bodies each morning. Despite its squalor, the Hive is where real information flows, and some of the city's most important residents choose to live here precisely because no one else would.
The Lady's Ward
The wealthiest and most heavily guarded district in Sigil. Grand mansions, faction headquarters, and the Armory line its clean, wide streets. The Harmonium patrols here in force, and the dabus maintain the buildings with meticulous care. Most of Sigil's power — political, magical, and financial — is concentrated in this ward.
The Clerk's Ward
Sigil's administrative center, home to the Hall of Speakers where faction representatives debate policy. Scribes, advocates, and bureaucrats fill its orderly streets. The Fraternity of Order maintains its courthouse here, and the Civic Festhall — operated by the Society of Sensation — offers experiences from every plane for a price.
Mechanus
The plane of absolute law — an infinite void filled with enormous interlocking gears that rotate with mathematical precision. Every surface is metal, every angle is exact, and every action follows predictable rules. Modrons march in perfect formation between gear-cities. The Guvner library here is a crystalline structure where knowledge is stored as pure logical formulae. Chaos is physically painful on this plane.
Limbo
The plane of pure chaos — a roiling maelstrom where earth, air, fire, and water churn together without form. Nothing has permanent shape unless a conscious mind wills it so. Githzerai monasteries float as islands of imposed order, and slaadi spawn endlessly in the elemental soup. Visiting Limbo requires constant mental effort to maintain a solid surface to stand on; lose concentration and the ground dissolves beneath you.
The Prison of the Mercykillers
A grim, towering structure in the Lady's Ward that serves as both courthouse and prison for those the Mercykillers deem guilty. Its iron cells hold prisoners from across the planes — fiends, celestials, and mortals alike, all judged by the faction's inflexible code. The deeper levels contain solitary confinement cells where inmates are subjected to silence and darkness for centuries. The astrolabe was hidden in the evidence vault, a chamber of confiscated artifacts.
Quests
Recover the Astrolabe of the Planes
The golden astrolabe, stolen from a murdered Guvner sage, is an artifact of immense power — it can map every portal in Sigil and may hold the key to understanding how belief shapes reality. Every faction in Sigil wants it. The party must track it down before it falls into the wrong hands, assuming there are any "right" hands for such a dangerous device.
Navigate the Faction Politics
Sigil's fifteen factions each have their own agenda for the astrolabe. The Harmonium wants to control all portals, the Xaositects want to destroy all order, and the Mercykillers want to hunt criminals across every plane. The party must forge alliances, make enemies, and decide whose philosophy — if any — they support. In Sigil, belief has literal power.
Prevent the Faction War
Tensions between factions have reached a breaking point. If the astrolabe is not secured or neutralized, Sigil will erupt into open warfare — and in a city where every doorway might be a portal to another plane, a war could destabilize the entire multiverse. The party must find a way to broker peace or remove the cause of conflict before it is too late.
Decipher Fell's Tattoos
The fallen dabus Fell has offered the party tattoos that serve as portal keys and protective wards. But his rebus-pictures sometimes contain prophetic imagery — visions of the Lady of Pain, crumbling planes, and a golden light that could be salvation or destruction. Interpreting these cryptic images may reveal the true purpose of the astrolabe and the Lady's intentions.
Encounters
Cranium Rat Swarm
In the alleys of the Hive Ward, a massive swarm of cranium rats — rodents with exposed brains that grow more intelligent in greater numbers — converges on the party. The swarm is large enough to achieve near-sentience, and it telepathically demands information about the astrolabe. If refused, it attacks with psychic blasts and overwhelming numbers, flowing through cracks and drains.
Modron March Disruption
On Mechanus, the party's investigation at the Guvner library triggers an alarm. A unit of rogue modrons — geometric beings that have deviated from their programming — attacks, believing the party is trying to impose chaos on the plane of law. Monodrones swarm while a pentadrone coordinates their assault with military precision.
Slaad Spawning Ground
In Limbo, the party stumbles into a slaad spawning ground where red slaadi are implanting their eggs in captured travelers. The slaadi attack in a shifting landscape where the ground, walls, and even gravity change without warning. A green slaad leads the group, using shapechanging abilities to deceive before striking.
Pit Fiend Incursion
A pit fiend leading a Baatezu strike team crashes through a portal into the Armory during the climax of the Faction War. The devil commands a squad of bearded devils and a chain devil, and it wants the astrolabe for the Blood War — the eternal conflict between devils and demons. The pit fiend is a cunning negotiator who may offer an alliance before resorting to force.
Balor's Gambit
A balor demon, representing the Abyssal interest in the astrolabe, smashes through the Armory's walls trailing fire and shadow. It fights with a sword of lightning and a whip of flame, filling the chamber with its death-throes explosion if slain. The balor cares nothing for philosophy — it wants the astrolabe as a weapon in the Blood War and will destroy everything in its path to claim it.
Factions
The Harmonium
Lawful Neutral
Sigil's self-appointed enforcers of law and order, the Harmonium believes that peace can only be achieved when everyone agrees — by choice or by force. They patrol the streets in red armor, enforce their rigid code of conduct, and run the city's jails. Their methods are authoritarian but their intentions are genuinely idealistic. They see the astrolabe as the key to imposing lasting order across the planes.
The Xaositects
Chaotic Neutral
The Chaosmen embrace randomness, disorder, and the creative potential of entropy. They communicate in scrambled sentences, make decisions by coin flip, and stage spontaneous riots they call "performance art." They are surprisingly effective because no one can predict them. They want to shatter the astrolabe and let the portals of Sigil open and close at random — true freedom, in their view.
The Fraternity of Order
Lawful Neutral
The Guvners believe that everything in the multiverse follows rules, and that understanding those rules grants power over reality. They are scholars, lawyers, and bureaucrats who study the laws of the planes with obsessive rigor. The murdered sage was one of their best researchers, and they want the astrolabe returned for objective academic study — though their definition of "objective" serves their faction's interests.
The Mercykillers
Lawful Neutral
Justice is absolute for the Mercykillers — there are no mitigating circumstances, no second chances, and no escape. They run Sigil's prisons and courts with iron-fisted efficiency. Their agents hunt criminals across the planes with relentless dedication. They want the astrolabe to create a multiverse-spanning surveillance network where no wrongdoer can ever hide. Their sincerity makes them terrifying.
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