Yellow clouds everywhere (possibly) except over the desert -- over a thousand feet thick -- exposure is toxic (though water breathing and a supply of fresh water will help against short term effects). Damage tends to be on the order of a hit point or two per round. The clouds are on the order of 1300 feet thick. Glowing streaks of cloud can be seen at night.
Swamp may manifest itself as many creatures...ogre magi [that do sonic attacks rather than cone of cold; same damage], shambling mounds, snakes, quasi-trolls.
Swamp also contains intelligent frogs, along with at least one green slaad. The frogs practice several forms of "jumping", including possibily teleportation and plane travel. (There are green slaad there too, and lilypads that seem to be used by frogs for transportation via Limbo.)
Will-o-wisps can also be found in the swamp, though we personally didn't observe any.
Wilhis are good creatures that live on hilltops in the swamp; ogres attack them but swamp creatures do not. (One hilltop had an astral presence above it which may keep the swamp at bay.) [Physical desc. of wilhis -- pancakelike with a face on one side and six spokelike legs -- noting their special abilities and bravery.]
Lizards...all six-legged, some intelligent; some walk on two legs, some on four, some on six.
Halfling monks in the desert (followers of Yondalla).
Dwarves underground all over (followers of Moradin).
No trees or similar plant life...magically grown trees show signs of damage after about a day.
Humans exist on the clouds of Xu, in the Walled City, and perhaps some insane ones in the Ruined City and desert area.
Rumors of an undersea city.
In the clouds: jellyfish with electrical and anesthetizing attacks, flying snakes that breathe lightning [possibly the snakes won here? see article on snake religion, same author], mantari-like creatures.
Soul-Furnace...where the fire giants use what little metal the world has.
The Walled/Perfect City...LN humans who maintain the floating roads and only let in other LNs. Regumark lives here, and the Chaosion is imprisoned here.
Floating roads connect Soul-Furnace, the Evil City, the Walled City, and perhaps other places; they are maintained by automata that resemble insects in appearance and hive mentality/comparmentalized functionality. The road is periodically "cleaned" by walls of fire. Rest areas with heat-resistant sleeping bags and access panels (locked, but hooked into a touch-pad system) at regular intervals. [Desc. of lanes, central ridge w/ encoded info.] Some guard stations are run by fire giants and orcs.
Undersea City (rumored)
Ruined City...in the desert; if any inhabitants, they're nuts. (Thrikeen is thought to be here.)
The Xu believe there are three entrances to this world...Good on the mountain, Evil in the Ruined City, and "intermediate" near the Walled City. Since we appeared in the Swamp, there appears to be a flaw with the theory.
Selemine has clearly been there, since all the mages (and perhaps priests -- the only ones we met were Moradin dwarves and Xus) are good.
Quillion is opposing the LE regime in the Orc Pits.
Regumark is in use in the Walled City.
Chaosion is imprisoned in the Walled City.
Asmodanu and Malefint are in use in the Evil City.
Thrikeen is presumably somewhere in the desert.