The hellhound was conceived based on ideologies of Greek and Roman mythology. Cerberus is a three-headed hound who guards the gates of Hades. In Tibia, they guard a path to the throne room of Infernatil. From this, the sprite was created. The name however came from both the description of Cerberus, and from clever wordplay: hellhound is also a demonic entity. These hellish minions are often considered to be guardians of the entrance to world of the dead or afterlife. Similarly in Tibia, they reside in the fiery depths of Pits of Inferno. These creatures appeared in the Winter Update 2006 when the Pits of Inferno were opened.
Their melee attack is considerable weaker than their wave attacks (which are fatal if shot together) so it's best to have a knight blocking it while standing diagonal. Magic Walls and Wild Growth can be used to help the knight in staying diagonal and preventing it from retargeting. These creatures are very strong so don't underestimate them: always have a good blocker and more than three shooters to slay them quickly. Use Ice and Holy based attacks. Not recommended to hunt these creatures. Possible great waste. Just kill them in Quests.