Hellhounds are fleet and have keen senses. Like demons, they speak demonic language. They are entirely fireproof - specifically, heatproof and noncombustible. Some hellhounds can learn to cast fire spells. Other than that, they have no special abilities.
After these basics, there are many possible mutations. A hellhound may be born with a third eye, or a snake's tail, or even three heads (the famous Cerberus being the only example of that particular mutation).
These mutations are nothing like mutation in DNA; each one was programmed in specifically (see Species History), and when a puppy is conceived there is a small probability it will show just one of the possible mutations.
magic. They can survive being frozen solid, though will lose consciousness.
Hellhounds speak and understand demonic language and also normal dog communication.
Their senses, agility and stamina are on par with normal hunting and coursing dogs, taking the hellhound's size into account, with one exception: they see in colour (though a skewed range, because their corneas are red).
They cannot shapeshift or have their shape altered by demonic methods.
himmelhunde) is supernaturally terrifying. It is described as causing terror in "mortals", which can be taken to mean roughly anything other than mosts kinds of demons, most angels and fullblown deities - it particularly includes ghosts and anything dead or undead, those being hellhounds' intended prey.
Hellhound howling tends to set up odd echoes that heighten the effect and make the sound seem louder. In enclosed spaces the effect can be awesome enough to make rational thought flee, while in wide open spaces the sound carries over great distances.
created by a group of ancient demons, none of which is thought to have survived until the Twine Wars era. This means, taking into account demons' uncommunicative nature, that there are no demons left who will admit to remembering where hellhounds come from.
Hellhounds were created from normal dogs imported into hell. After a selective breeding project was abandoned -- demons are very impatient -- a group of geneticists combined dog DNA with demon genetic material.
Carbon-based lifeforms' genetic material is nothing whatsoever like demon DNA. Manipulating other lifeforms' genes is an extremely advanced skill. Combining one with the other is ludicrously difficult.
Against flabberghastingly huge odds, viable lifeforms were eventually created through this process. They were mentally unstable and had various other problems, some of which were ironed out. The stability issue was eventually glossed over by introducing a characteristic that forces each hound to bind to a demon in a subordinate role. This suited the purposes of the designers, who wanted wonderful (and, above all, obedient) pet/companion/bodyguards.
Hellhound mindbonds are built on the standard demonic system, but skewed. For more detail see Mindbond (Demon).
Hellhounds are not romantics. Hellbitches come into season about once a year, for a few days. (This generally makes them even more irritable than usual.) The female will select her mate more or less at random, usually with a growled "Hey you". Mating takes place with much snarling and biting, after which the female forgets about the male pretty much immediately.
Approximately one mating in three results in pregnancy; hellhounds are not very fertile, probably because of all the genetic tampering (see Species History). The gestation period is around five months. Normally only one puppy is born; on rare occasions there may be twins. A hellbitch can't physically carry more than two pups to term.
The pup's eyes are open by the time it is born, and it can stand within minutes. Pups are generally weaned and ready to leave their mother by the age of two months. Usually a hellbitch will not breed again for one or two menstrual cycles. Hellhounds are not naturally maternal.
Although they are weaned early, hellpuppies have a relatively long childhood. They take about six years (by human standards) to reach adolescence, although their brains develop more quickly, and it'll be four more years before they are physically mature. It takes a while for body to catch up with mind. This too could be seen as genetic-engineering negligence.
They can be abbreviated, as in Chokedamp Pepper-Shriker. This is a matter of preference but can irk some hellhounds, especially ones proud of their lineage.
Hellhounds with braggable lineage may include grandsires' names, or even great-grandsires', as in Chokedamp sired by Pepper-by-Barkley-Brandog-Bau-out-of-Rhymni-Siaw-Brath daughter of Shriker-by-Morty-Big Grim-Giver-out-of-Hellgast-Nuby-Zayin Alpha Release. Beyond this, it gets silly and you need brackets.
Hellhound pedigrees are represented in Twine in table layout, with the female ancestor always below the male. The unbroken female line is considered most important, such that reading the very bottom name of each column gives the hellhound's most braggable lineage.
See also: Demonic Names