Nine Hells

The Nine Hells -- also called Baator or simply the Hells -- are an Outer Plane that is home to devils and the souls of the damned. Their overlord is Asmodeus, who rules the plane from the Ninth Circle at its center. The Hells are a prison plane of sorts, created near the dawn of time to stop Asmodeus and his minions from gaining control of Creation. The devils who reside there play a part in the divine plan of those who made the plane, taking custody of the souls of evildoers -- though the devils have long interpreted that mission to include turning mortals to evil in order to collect their souls later. The plane's nature is lawful evil, matching the alignment of its infernal residents.

Because the Nine Hells is a prison, devils -- with the exception of imps, their designated messengers -- cannot leave the Hells of their own volition. They can, however, be invited onto other planes by those planes' denizens, and can stay for a time, more or less at the sufferance of their summoner. Because such summonings are usually quite magically intensive, and because devils are crafty and seek relentlessly to exploit their summoners, mortal arcanists rarely summon a devil in a high-leverage situation such as combat when a demon would do; instead, mages truck with devils when they seek knowledge, counsel, or best of all to make a bargain.

The circles of Hell include:
 * The First Circle Avernus, a charred wasteland ruled by either Bel or Zariel, depending on which account you believe.
 * The Second Circle Dis, best known for the great Iron City of Dis and ruled by Dispater.
 * The Third Circle Minauros, an oily bog and soul-trading hub ruled by the rapacious Mammon.
 * The Fourth Circle Phlegethos, a land of flames and liquid fire, ruled by Belial and his daughter Fierna.
 * The Fifth Circle Stygia, an ice-covered ocean roamed by great beasts and ruled by the imprisoned archduke Levistus.
 * The Sixth Circle Malbolge, prison of rank caverns interrupted occasionally by gardens of startling but corrupt beauty, ruled by Glasya.
 * The Seventh Circle Maladomini, fly-choked land of ichorous ruins, ruled by Baalzebul.
 * The Eighth Circle Cania, arctic wasteland anchored by the glacier Nargus, ruled by Mephistopheles.
 * The Ninth Circle Nessus, a varied melange of the worst of the other circles, ruled by Asmodeus Himself.