The Night World is a dimension first mentioned in the Insylum RPG, though it owes much to the author Dennis Detwiller's Delta Green RPG adventure, Night Floors.

As such, if you've not played through either of the scenarios, it's a good idea to steer clear from reading this, as it will most likely provide a lot of spoilers.

What Is The Night World?

It's hard to pin down. Is it a dimension where The King In Yellow's presence creeps out and snares building, cities, perhaps whole worlds as the madness of the play spreads? Or is it some aspect of the collective consiousness, built up by the experiences of those mad people who've lost their minds to the King and his play? In any case, the game describes it as follows:

The Night World is the result of the Play — the pivot on which the world was set — while the real world is nothing more than a still reflection of the madness that lies at the heart of it all...

This is not some dry tour through a shifting maze of rooms; it is a coherent flow of insanity, ridden like a roller coaster. Ideas grow; shift and change like monstrous plants, and sometimes even consume their creators...

The Night World expands forever. There is nothing it cannot encompass, be, or do. It is larger than all the worlds that ever were. It is in the truest sense, infinite. It is the liquid substance of the imagination made real when it is observed. Before it is solidified however, it is simply that — liquid and shifting and indistinct — insubstantiality waiting to be made real by the mind of a madman...

In Insylum it is only possible to enter the Night World when, at midnight, doorways open up to it. The visitors always return the last second before 12:01, if they return at all.

The Sets

The Night World is made up of a number of 'Sets' - as befits a play.

The sets provided with the main rules are as follows:

The Castle

At the edge of The Lake, at night, masked guests walk through the gates to a fairy-tale castle, on their way to attend a party. They wear many costumes and speak many languages.

The Party

Past the guards in lion masks the party is in full swing. Rumours abound about The Phantom of Truth and the King In Yellow until the clocks strike midnight, and the party-goers fates are revealled.

The Lake

Presumably Lake Hali, the lake is a misty lake that doesn't really contain water, and seems to hold strange secrets in its depths.


In Insylum the city of Carcosa is a sprawling city that surrounds The Castle, "Caught somewhere between Victorian England and Gaudi Spanish architecture, it’s a sprawling town of many levels, plazas and vistas; shrouded in mist and always consumed by night." It is the hub of the Night World, linked to every other set and, presumably, where everyone stumbles into before they discover The Castle and The Party. Considering Carcosa is traditionally the King's city across the lake from the party, have the names of Carcosa and Yhtill been swapped over? Or has the former replaced the latter, condemning Yhtill to sit elsewhere, isolated and tomb-like.

The Broadalbin Hotel

A hotel in 1920s New York, from the story Broadalbin.

The MacAllistair Building

The apartments in modern day Manhatten, from the scenario Night Floors.

The Whisper Labyrinth

A series of underground tunnels, with walls lined with alcoves, each alcove to house a bottle, each bottle assigned to a different person. Somewhere, if you search long enough, you will find your name, your bottle.

The Library

A strange library that seems to have reverted to a wild state - lights that fade on and off as with the passing of the sun, evidence of camp-fires, and a mysterious creature stalking the aisles by night.

The Clockwork Factory

A grand deserted factory that appears to manufacture life-like porcelain mannequins. The sound of haunting violin music can be heard from behind a locked vault door.


An ancient city, "looks like a cross between classical Rome and Mesopotamia, rich with former glory and opulence" - where stone statues of lions adorn every surface, disturbingly with their eyes scratched away. The Yellow Sign is daubed on various flat surfaces too. The city seems deserted.

The Players

This is the term given to the mysterious figures that haunt the Night World. They are split into four sections:

  • Figments - pretty much ghosts, who leave clues of their existence behind, but rarely appear directly to people unless on their own...
  • Repeaters - like ghosts but with no personality, repeating their final acts, such as the central characters of the play. Strange then that Repeaters can be dispelled forever, if confronted correctly...
  • Creatures - Pretty much animals (or monsters), Creatures are motivated by instinct - be it food or shelter...
  • Entities - Those who have retained their personalities, despite being claimed by Carcosa - as well as he who rules over them all, The King In Yellow...


Some parts of this version of The Carcosa Mythos don't mesh well with what is detailed elsewhere - for example, the character normally known as Cassilda seems to have become Cassandra, whilst her daughter Camilla is now Cassilda.

Additionally, the King seems to quote things that are actually spoken by The Stranger in traditional texts - although its fair to say there's always been a close link between the two characters.

Are these errors due to a misreading of the original texts? Or do they symbolise a madman's failure to grasp the true nature of the Play?

Community content is available under CC-BY-SA unless otherwise noted.