- "Fetch me their souls!"
- — The Demonic Announcer at the beginning of a Hellhound round.
The Hellhounds are an aggressive and murderous type of zombie that are encountered on their own special round in Shi No Numa, Der Riese, Kino der Toten, The Giant, Der Eisendrache, Blood of the Dead, and Classified. They also make additional appearances in Dead Ops Arcade, Moon and Green Run.
Hellhounds are essentially zombie-dogs that are a mutated version of Samantha's pet, Fluffy. Fluffy was put in the Der Riese mainframe teleporter and turned into a deadly Hellhound. She later had puppies, accounting for the rest of the Hellhounds. Hellhounds resemble badly deformed German Shepherds. They randomly spawn throughout the map (a ball of lightning will usually indicate whenever they spawn) in packs of two to four (depending on the amount of players) every four to five rounds and their sole objective is to kill the player by attacking with their teeth and claws or by exploding after death. The ground shakes whenever they spawn and there will be a heavy fog covering the map. There are two variants of the Hellhound: the flaming Hellhound, which on top of being perpetually on fire will explode on death, and the normal Hellhound, that simply falls to the ground and will not explode when killed. When the last Hellhound in their special round is killed, it will always drop a Max Ammo power-up. One exception to this is Shi No Numa, where the Max Ammo may not be dropped by the Hellhound, but the next zombie the player kills. The electric bolts that appear during a Hellhound round are supposedly linked towards the teleporter incident that occurred at the Der Riese facility.
In Green Run, through a Custom Games lobby, the host has the ability to turn on/off a Hellhound round if the host has selected a Survival or a Grief game mode map. The only maps that are available for Hellhound rounds are Bus Depot, Farm and Town.
In Der Riese, there are a series of radios that depicts the Hellhound's creation. Dr. Maxis and his assistant, Edward Richtofen, were doing tests at the Der Riese facility. One of the tests involved Samantha's dog, Fluffy. When teleported, Fluffy vanished and later reappeared as a demonic variant of Samantha's dog; Fluffy became a Hellhound. When this occurred, Richtofen followed through with his plot to get rid of the Maxis' by locking them in the teleportation laboratory with the possessed Fluffy and sending them through to the Aether. Dr. Maxis was teleported to an unknown location, while Samantha was sent to Griffin Station. Samantha seems to now control the Hellhounds as she attempts to kill Richtofen. One of the radio messages hints that Fluffy was pregnant, explaining why there are multiple Hellhounds.
- Shi No Numa
- Der Riese
- Kino der Toten
- Dead Ops Arcade
- Green Run
- Bus Depot
- The Giant
- Der Eisendrache
- Blood of the Dead
- If one uses Insta-Kill to kill the last dog of a round, they will not drop a Max Ammo.
- Hellhounds will attack certain players and do not switch between targets until the one they are after is downed.
- In Der Riese, there is a door with a warning sign and a Hellhound head nailed to it. On the floor inside of the door, there is a lot of blood.
- In Der Riese, if a teleporter is nearby during a Hellhound round, many Hellhounds will spawn out of the teleporter.
- On Call of Duty: Black Ops (Nintendo DS), there is no specific Hellhound round. Hellhounds can appear from round five and have increasing likelihood of appearing each round. These Hellhounds only spawn coming from barricades like zombies, and will knock down the barricades by jumping on them.
- In Der Riese, Dead Ops Arcade, Moon, The Giant, Der Eisendrache, Blood Of The Dead, and Classified they can appear alongside the zombie horde.
- Hellhounds were set to appear in "Five", since there are character response quotes for them in the game's files.
- In the game files there is a scrapped audio file with the name
mx_dog_wave_b, suggesting there was to be a song played during the Hellhound round.
- A part of "Beauty of Annihilation" plays at the end of a Hellhound round in the World at War and Black Ops versions of Shi No Numa and Der Riese, as well as Kino der Toten, Green Run and Classified.
- Dempsey snickers "Devil Dogs" at times upon a Hellhound round, a reference to the nickname, supposedly given by the German military, to the U.S. Marine Corps.