Humans
They don't need description, you are one...
Dragons
The dragons, the oldest race on earth, though to be merely a fantasy creature for thousand years, are now proved to be real. During the last centuries, the dragons took the decision to hide themselves from the humans, who were becoming more and more dangerous by developing new weapons with very quick rate. However, since the Apocalypse, the dragons have returned. Biggest dragons can reach 30 ft tall, and some are slightly taller.
Mutants
Mutated humans or animals, they are very different from each others. Have imagination with them, and all creatures that are not humans or dragons are mutants, but they can be nearly anything, so...