Carceri

Carceri is one of the Outer Planes of the Planescape. A plane-sized prison, Carceri is designed for individuals to enter and never leave. It is implied by Gamiel and The Broker of Sigil that the stronger an individual is the closer they are watched by Carceri's guardsmen.

Othrys
A layer of rusted iron and prison cells, Othrys is a maze of peeling metal and eternal conflict as various groups attempt to lay claim to section of the layer as their own territory.

Cathrys
An overgrown forest, Cathrys is less populated than Othrys but no less dangerous. Instead of watching for other prisoners who want to incapacitate you, the entire plane itself wears down prisoners by restraining individuals with vines and poisonous spores. Though the vines are easy enough to avoid just by walking, no one can walk forever.

Nybras' Lair
A growth of intertwining trees, Nybras lived in the little haven for years upon years.

Notable Residents
The Cyclops - A symbiotic relationship between an Aberration in the shape of a spider-like eye and a hulking creature with no eyes of its own