Chaos is, naturally, the god of chaos, evil and destruction. He lives to destroy. He is sadistic and loves to see things crushed by his own willpower.
Chaos appears as a cloud of roiling storm clouds, scarlet lightning and dark matter. He has two bright lights that serve as eyes, even though he doesn't really need them.
Chaos is sadistic and cruel. He loves to see things break. He is completely incapable of any sort of empathy, and all his emotions are twisted - sadness is jealousy, anger is hatred, love is lust, etc.
Chaos is able to destroy any solid, liquid, gas, plasma or other things on a whim. He breaks them down to a sub-atomic level, whether alive or dead, never to be seen again. He, however, cannot die either. Or, at least, it is very, very, very hard to kill him.