Planescape
Planescape is an official D&D campaign setting first introduced in Second Edition. The setting centers around exploring an original multiverse cosmology.
Planescape cosmology
Sigil
Sigil is a city built on the inside of a torus (imagine a tire laying on its side with buildings all around the inside of it). From anywhere on the Outlands (the most neutral of the Outer Planes), Sigil can be seen floating above the great stone Spire, but since the Spire is infinitely high, the only way in or out is through the portals that manifest themselves inside of doorways, windows, and any other kind of bounded space inside Sigil. Because of this, Sigil is also called 'The Cage'.
Portals like those in Sigil exist all over the multiverse, linking distant planes to each other, but the concentration is highest in the Cage. This phenomenon makes Sigil one of the most coveted locations in the multiverse. Gods and fiends would love to take over, but Sigil is guarded by a being called the Lady of Pain, whose diligence bars would-be conquerers from entering the city.
Prior to the events of the Faction War adventure, Sigil's political and philosophical system is dominated by fifteen factions, all vying for the most believers (see Factions, below).
Inner Planes
The Elemental Planes (air, earth, fire, and water) are the most famous Inner Planes, but there are many other planes traditionally grouped into this category. These planes are:
- The Positive and Negative Energy Planes (realms of pure "healing" energy and the force that powers undead, respectively).
- The Paraelemental planes (such as Magma, the intersection of Fire and Earth, or Ice, the intersection of Water and Air).
- The Quasielemental Planes, formed from the interactions of the Positive or Negative Energy Planes and the planes of Fire, Water, Air, and Earth (such as Vacuum, formed from Air and Negative Energy, or Mineral, formed from Earth and Positive Energy).
Outer Planes
There are seventeen Outer Planes, each formed from the moral and ethical alignments of the sentient beings in the multiverse. Most of the Outer Planes are divided into layers; the majority of portals deposit beings on the first layer of the plane. Most of the gods (or 'Powers') in the multiverse reside on the Outer Planes, in lands called realms that are under their direct control. The Outer Planes are:
- The Abyss (chaotic evil).
