Hellhounds are genetically-engineered predators found throughout the Imperium of Sidhae and commonly used as working animals.
Considerably larger than a Siberian tiger, with a shoulder height of 180 cm and weight approaching 500 kg, clad in a thick coat of armored scales and equipped with a pair of demonic luminiscent pupilless eyes, a hellhound is a truly terrifying creature to behold, especially when not separated from it by sturdy bars.
It's massive size, power, terrifying appearance, armored scale coat and vicious temper make it a fearsome opponent, so various Imperial institutions use hellhounds as attack dogs. Hellhounds were genetically engineered on a canine DNA basis sometime in the 23d century and have since proliferated throughout the Imperium, escaped specimens forming feral populations on numerous worlds.
Being a creature designed for combat and guard duties, the hellhound is strong, agile and extremely aggressive, yet possible to tame and train. While retaining a lot of it's original canine traits, such as pack mentality, keen sense of smell and general dog-like behaviour, it also incorporates some feline traits, as is evidenced by it's gait and excellent night vision. The hellhound's most alien feature is it's coat of scales, thick enough to resist small arms fire and most melee attacks.
Hellhounds are by nature very loyal to their pack, so if raised and trained from a young age by a Sidh or human, they will normally be very docile around their owner, but fiercely protective of him and distrustful of any strangers, making them excellent guard animals. If properly socialized and trained from an early age, a hellhound will be no different from an ordinary, if a very large dog, and pose no more danger to strangers than ordinary dogs would. A group of hellhounds, however, will form a pack hierarchy among themselves and turn on their handler unless he establishes himself as an undisputed leader of the pack. Due to the hazards inherently involved in this, humans rarely take hellhounds as pets in any number, an augmented Sidh in powered armor being much better equipped to impress his authority upon an unruly beast of such size and power.
The most obvious feature of hellhounds is their armored scale coat similar to that of Terran pangolins. The genes responsible for this coat, however, originate from an unspecified extraterrestrial source rather than any Terran animal, as is evidenced by their composition, significant degree of mineralization making the scales considerably tougher than the plain keratin ones found in pangolins. These scale coats are thick and tough enough to resist gunfire. The scales also serve to indicate the hellhound's emotional state, rising on end and changing colour from dark grey to red especially around the neck when the hound is agitated. An agitated hellhound is also capable of rattling the larger scales on it's shoulders, neck and back, producing a sound not unlike that of a rattlesnake in addition to it's normal canine growls and snarls.
Another feature inherited from the hellhound's xenogenetic aspect are it's pronounced dewclaws, which serve both as climbing aids and hunting tools, impaling and eviscerating prey. Given this and the feral hellhounds' preference for rocky, mountainous habitats in the wild, the alien DNA source for the original hellhounds was probably a scaled mountain-dwelling creature hunting other creatures with a similar scaled armor, the long dewclaws being quite effective of jabbing under the scales and into flesh, tearing up a wound where to bite afterwards.
Hellhounds mate once a year and usually have four to six pups, who mature in four years.
As working animals, hellhounds are most often seen accompanying Domestic Security troops and guarding DomSec and military installations. A cyber-augmented variant, known as cybhound, is occasionally employed by the military. While much easier to train and control, cybhounds also lose much of their natural qualities in the augmentation process, becoming little more than mindless (if no doubt still terrifying) organic combat drones, Domestic Security preferring the raw, unadulterated viciousness of regular unaugmented hellhounds.