Hellhounds

"Hellhounds. Demonic pit bulls." -A hunter
Hellhounds are ballistic and maniacal canine-like beasts of the supernatural world, specifically Hell (hence the name), which are known to serve Demons. Described as demonic pit bulls, Hellhounds are ferocious, terrifying entities that inspire fear in Humans, Demons and even Angels.
With time they became tasked with collecting the souls of humans whose deals are come due. In such circumstances, Hellhounds can only be seen by those whom they have come for, making them sort of a Reaper of the damned.