Sigil

Sigil is a demiplane, comprised entirely of a city of the same name. It is sometimes known as the City of Doors, as it is said to contain portals into every other plane. It is ruled by an enigmatic figure known as the Lady of Pain, about whom little is truly known for certain save that she has forbidden any deities from entering her city. As there are no known cases of a deity violating this rule, it is speculated that she has found a way to physically or magically prevent their entry.

The Lady of Pain entrusts her servants to run the city, and while minor crimes are beneath their notice, any disturbances that threaten the city itself are swiftly and severely punished. As a result of its position as a hub between planes and the Lady's laws, Sigil is seen as a place of neutrality and is frequently used as a safe place for opposing planar factions to negotiate. The Lady of Pain's servants themselves are made up mostly of angels, devils, demons, and other extraplanar beings who have foresworn their usual allegiances in order to serve her, and Sigil, instead. Such servants are typically identified by the Lady of Pain's crest worn somewhere on their person; those outside of her employ who attempt to use her crest to pass themselves off as such will quickly meet a very grisly--and very public--demise.

Sigil is built inside of a massive, miles-wide torus floating in empty space. The inner side open to the sky, which is filled with stars and appears to stretch endlessly in all directions. The city's size is not fixed; many scholars have attempted to measure it, and received wildly differing results. Theories abound as to whether this is a natural phenomena of the demiplane or something dictated by the Lady of Pain herself. At the center of the open space within the city's center is a massive pillar of polished stone, its ends vanishing out of sight in both directions, known as the Axis. Nothing is known about it beyond what can be observed from the surface, as flying servants of the Lady of Pain guard it at all times. Any who approach the Axis are given a single warning to turn back, and no quarter is given to those who fail to heed it. Though there are many theories as to the purpose of the Axis, it has thus far been impossible to confirm anything.