Hell Hounds are Lupine/Reptilia hybrids, bred for speed and strength in "The Pit" on Kantor Boralis. In the last 20 cycles, the Slam Security Network has been adapting the hounds for "enforcement" in the sector's penal system. For security purposes (as well as for the guards' amusement), they are periodically released into the Slam Facility at "feeding time", where they indiscriminately attack and devour any inmates that have been unable to reach safety in time.
When enraged or attacking prey, the colors of their scales change from black to an orange/red. Riddick was able to tame a Hell Hound during feeding time, leaving The Guv perplexed as to how he had accomplished such a feat, to which Riddick replied "It's an animal thing."
The eyes of the Hell Hounds have properties very similar to Riddick's.