Reavers are humanoid but bestial in appearance. They live for war and are violent in the extreme. When they can't find any enemies of other races they will fight among themselves. They serve the Armagons but they also tend to be pirates and shatrats, raiding and murdering space-stations, ships, colonies, planet habitats ans so on. They are extremely hostile to all other species.
Source: Shatterzone Universe Guide
Related: Reavers (Firefly?)