"There is no room for '2' in the realm of 1's and 0's, no place for 'mayhap' in a house of truths and lies, and no 'green with envy' in a black-and-white world."
- A donut shaped city in the sky run by the (not-a-god) Lady of Pain.
- Not set on the Material Plane; the city is a crossroads.
- Random portals to other planes exist.
- Philosophy-derived factions take things to the extreme.
- Things happen in threes and return to where they started.
- The nameless one (player) is continually reincarnated.
- Written in Cant - a kind of slang.
- Lots of races - if its sentient and not a god, its here.
- First appearance of the tiefling, githzerai, aasimar and genasi.
Planescape is a campaign setting for the Dungeons & Dragons fantasy role-playing game, originally designed by Zeb Cook. Planescape "solidified the Great Wheel cosmology that began in 1e and would later be reinstated in 5e as the dominant of three theoretical models". Planescape links other Dungeons & Dragons worlds via inter-dimensional magical portals.
The game is set in Sigil, the "City of Doors", a torus shaped city/world that rests atop the Spire. There is no sky, simply an all-pervasive light that waxes and wanes to create day and night. Sigil cannot be entered or exited save via portals. Thus, many call Sigil "The Bird Cage" or "The Cage." There are fifteen philosophy-derived factions. Each of these factions is based on one particular belief system; one faction's beliefs make them enemies while others make them allies. There are three principles (or heuristics) governing the world of Planescape:
- Rule-of-Three: Things tend to happen in threes.
- Unity of Rings: Things are circular, coming back around to where they started. This is true geographically as well as philosophically.
- Center of All: There is a center to everything—or, rather, wherever a person happens to be is the center of the multiverse...
Note: A Planescape tradeable card game was published under the title Blood Wars.