The Hellhounds are a fairly weak, yet highly aggressive, fast-moving, and admittedly frightening looking enemy first encountered in Shi No Numa and later featured in Der Riese, Kino der Toten and Moon. They also return in Green Run as an option for Custom Games. They are deadly dog-like monsters covered in flames that are the mutated puppies of Samantha's dog "Fluffy". They randomly spawn during their own, exclusive round and can appear anywhere on the map (a ball of lightning will usually erupt whenever they spawn) every 5 or 6 rounds. Their sole objective is to kill the player by rushing towards them and either attacking with tooth and claw or (rarely) by exploding. Though Hellhound attacks are weaker than those of a normal zombie, Hellhounds are much faster. Furthermore, on Der Riese they will also appear during regular rounds beginning on round 16, 17, or 18. The ground shakes slightly whenever they spawn or explode. They are difficult to outrun, especially in groups, and must usually be eliminated as soon as possible. On Moon, Hellhounds only appear in No Man's Land and even then, only after the alarm sounds during each visit. However, they can spawn without limit.
On Der Riese, there are a series of radios that can be turned on, two of them have the sounds of dogs in them. One of them is a recording of an experiment on a dog, using some sort of electrical chamber. The people who are experimenting sound German (maybe Nazi Scientists that are experimenting on, and maybe even had started the zombie outbreak). After the experiment, one of the scientists (known only as Doctor Maxis) tells his assistant to open the door (The assistant is Doctor Richtofen, referred to as "EDWARD!"), the assistant hesitates, Maxis snaps back to him and the assistant opens the door. The sound of electrical swirls and a Hell Hound can be heard, afterward a little girl can be heard saying "Father, what are you doing with Fluffy?" (The girl is Samantha Maxis the demonic announcer). Maxis replies with "Damn it, Samantha, I told you never to come in here!", shouts to his assistant to remove Samantha from view of the dog. Samantha screams at the sight of her dog (formally known as Fluffy). She says "What is wrong with her? Daddy, what did you do? Fluffy!", Before running off. Maxis replies "Come back here Samantha. Stop Her." Maxis runs after her, while saying "Easy, come here Samantha. Good girl. Gently Samantha, we must get out of here" (all through that sentence, the Hellhound seems to have got out of the chamber and is destroying equipment and windows.) Before Maxis and Samantha have a chance to get out of the room, the assistant seems to have locked the door behind him as he came out. Maxis shouts "Edward! What are you doing?! Open the door! Edward! Open this door now!". Samantha cries "I'm scared". Maxis says to Edward "Damn you, stay by me Samantha". Then the assistant speaks "Goodbye, Doctor Maxis!" in a voice very similar to Doctor Richtofen. A teleporter activating seems to be heard before Edward laughs in an evil tone. After that, the message cuts out into static. Samantha, Doctor Maxis and The Hellhound (Fluffy) are teleported to Griffin station on the Moon.
The Hellhounds gained the use of telapotation when they first went though MTD, but even with that power they cannot teleport to the moon itself.
- "Those don't sound like freak bags." - Tank Dempsey
- "Shit!... Here come the dogs!" - Tank Dempsey
- "The Devil's Dogs, no match for the U.S Marines!" - Tank Dempsey
- "Man's best friend? I don't think so!" - Tank Dempsey
- "Fuck you Fido!" - Tank Dempsey
- "I hear some angry fucking dogs!" - Nikolai Belinski
- "The air hangs heavy with stench of dog shit!" - Nikolai Belinski
- "The spirits are toying with us!" - Takeo Masaki
- "Die! You diseased dog!" - Takeo Masaki
- "My flesh will not be consumed!" - Takeo Masaki
- "Fluffy? Is that you?" - Doctor Richtofen
- "Poor puppies, they know no better." - Doctor Richtofen
- "Something is coming through!" - Doctor Richtofen
- "the worlds, they break in two!" - Doctor Richtofen
- "Down, cyka! (Russian for bitch)" - Nikolai Belinski
- "Fetch me their souls!" - Demonic voice, every time Hellhounds spawn
- "What did you do to the poor puppies?!" - Doctor Richtofen
- "Mommy said not to hurt the little animals any more." Doctor Richtofen
- "You don't want to eat my soul; it probably tastes like vodka... Mmmm... vodka."- Nikolai Belinski
- "That's the last leg you are ever going to hump" Tank Dempsey