Voor

"This hulking creature waddles towards you on stubby legs. It's enormous arms end in vicious claws. Its armored face has no eyes, and ropelike tentacles constantly shoot out from its arms and back.—Monster Manual IV"

Voors, known to other fiends as "lashers," are hulking, brutish yugoloths used as guardians or as protectors of fixed areas. They have also been seen as bodyguards or enforcers for more powerful fiends.

Ecology
Voors have ravenous appetites for flesh and even greater appetites for blood; the legacy of cruelty and murder they leave behind makes this obvious to those who have witnessed their rampages. Periodically a voor may spawn broods: it takes five years for a juvenile voor to reach maturity, after which it is ready for guard duty. For a long time the voor will stick close to the voor that spawned it, learning techniques for guarding an area and capturing prey.

Society
Voors serve more powerful fiends because they're tough and dangerous enough to be effective, yet dim-witted enough to take orders without question. The voor is incredibility patient, as it can be content to sit and guard an area for weeks, waiting patiently for the opportunity to cause destruction and havoc. Due to its simple intellect, a voor can only comprehend simple commands like "Guard this area" or "Permit only humans who say 'Orcus' to pass"—anything more complicated is simply lost to them. Unless told otherwise, the voor will pursue and destroy lesser fiends who enter the area it guards. The unfortunates that fall will have their corpses laid out as a warning to other trespassers. Though the voor is more subservient then most fiends, it still delights in the bullying of lesser creatures. Perhaps this is a way to express their blood-lust.