The Fallen are made up of many different races and creatures. Some of these creatures are sentient (or semi-sentient). Some are mindless and others, while lacking sentience have a cunning that makes them lethal.
This is by no means a complete list of Fallen creatures.
Trolls. Huge, powerful, stupid. Powerful sorcerers can charm them.
Edars. Rare but powerful Edars are incredibly dangerous with their elemental magic. Can be recruited – for a price.
Umderdroths. The Dread lady Umber bred these lethal killing machines as pets. Can be tamed by powerful channelers.
Daemons. No other way to classify these nightmarish creatures. Created by the Titans, they may be immortal.
Sions. Powerful users of a very specific magic. They can be recruited.