Death's Dog is Death's dog. He collects canines when they pass away. He shares the same voice as Death, but unlike Brian, stands on four legs.
he looks like a f*****g 3-D dog
Death's Dog has only appeared in one episode so far, Mr. Saturday Knight, where he arrives with Death thinking that he needs to take Brian, who temporarily choked on a dinner roll. Death's Dog: Hey, somebody choke on a roll in here? Brian: Oh no, I spit it out.
Chris (to Brian): I don't have to listen to you! You're just a dog, you don't have a soul!
However, as Chris is an unreliable narrator, he probably does not state a rule of the Family Guy universe.
- FG309 "Mr. Saturday Knight"