The Nether Map
Season 2 of our Quorum of Bones campaign started with the players thrown into hell, which I called the Nether. The center of the map held the perpendicularity, which was a Neverending Story style tower that had a portal between realms. It was controlled by a group of not very nice lawful good angels.
The surrounding lands were all controlled by various devil lords, which I only revealed as the players explored the lands.