There are many sentient races on Sky World besides humans. Being a typical fantasy setting, there are of course elves, dwarfs, dragons, Orcs, and goblins. There are also semi-sentient races such as bugbears, and such. Given the geography of Sky World, none of the races were likely to have evolved on Sky World. The Gods might have created them though.
Humans are the politically dominant race on Sky World. Sky World humans are the same as Earth humans except that psi powers are fairly common and obviously powerful.
Elves are typical fantasy elves. They are long lived and generally match the rules for AD&D elves. All elves have psi powers and take the same education limitation as human psis.
Dwarves are typical from AD&D. They are moderately long-lived and short. Since there are no mountains on Sky World, there have been changes from AD&D rules or their mythological basis. Dwarves are still miners, but mine more flat land burrows than mountains.
Half-Elves are half human and half elf.
Trolls are per Disc World. Trolls are one of the few sentient races on Sky World that are truly native. Trolls are silicon based life forms. Trolls are normally found only in the northern sections of Sky World. As the ambient temperature rises, trolls get stupider. This drop in intelligence is based upon troll brains being silicon based, similar to a computer. Trolls are also nocturnal creatures. Contact with sunlight, unless special blocking compound is used, will turn a troll into rock. They will re-animate when the sun sets. See also wights, which are the Sky World version of Norwegian Trolls.
Winged Folk are basically humanoids with wings.
Wights are short furry creatures of extraordinary ugliness. They live in wilderness wood areas. They are based upon Norwegian trolls. They are short, generally less than 3 feet tall.
There are a large number of semi-sentient races on Sky World.
Tarns are a form of large bird. They can travel many hours with a human on their back. This gives them a range of up to 200 kilometers. Idea is from Gor series by John Norman.
Zombies on Sky World come in two varieties. The first is based upon "Night on Mispeck Moor" by Larry Niven. The dead are animated by a bacterium / plant. When a person dies, if they are near one of the plants, the plant will drop a seed. The seed sprouts in a few hours and the zombie will both travel and attack that night. In the morning, the zombie will drop and the plant will take root in the body and grow normally. Zombies only occur on the first night after death and can be killed by a heal sickness spell. A body can be prevented from becoming a zombie by pickling in salt water or in alcohol such as wine or beer.
The second variety of zombie is actually sentient. It is based upon the Disc World zombie.