3 locations

Planes and Planets
Borlus is a small plane floating in the astral seas. It is a perfect disc, 1000 miles from edge to edge. Ambient light equivalent to terrestrial twilight pervades the place, and the air has a slight haze, keeping maximum visibilty to 300'. X-Ray and Ultrvision do not function in Borlus. It is ruled by the powerful demon lord Agsa (HD 11+3(hp ) AC -4 MV 15"/15"), who pays little attention to his domain, so long as his manes preserves and citadel are undisturbed. Agsa is a powerful mage (magic user level 15) and has invented many powerful variations of spells (changing Monster Summons spells into Agsa's Summons spells, Agsa's Poisoned Web, etc...). Agsa can sometimes be convinced (or coerced) into teaching magi these spells in a painful instantaneous method that will replace the original spell and decrease constitution by one point.

Haarlusk is a tidally locked planet, the bright side scorched and desolate, the dark side a ice and rock waste with little to no atmosphere. The habitable areas of the planed form a ring running along the tropics of the transition zone. The weather is chaotic and often very violent. The sentients of Haarlusk are generally of three varieties: 1) insectoids under the surface of the bright side, 2) reptilians on the brightside surface, and 3) cold elemental creatures in the tropic of the transition zone, with no need of breathing.

Petchko 7 is a colony ship, long stranded but still functional, in deep space. It has been occupied by the demon Kalabus (HD 7 (hp ) AC 1 MV 9"), and he spreads cursed teleportation scrolls among many worlds. Kalabus has reprogramed the Petchko 7 to provide a suitable deathtrap for those unfortunates brought to it. Clerics and druids will not have access to spells higher than 4th level from their deities, short of gates or other direct contact. When those telepoted in are too dangerous or powerful, Kalabus may apologize and offer to teleport them home if they will then disseminate three scrolls of cursed teleportation where they go. There is only a 30% chance that they will be returned to their plane of origin, though, as Kalabus prefers his traps to be widely spread.

(yes, I am just kinda data dumping these days.)