A Wirewolf is a monstrous Chaos machine in the service of Magister Anakwanar Sek's forces. They are powered by a trapped daemonic entity, in the same fashion as a Defiler, but can take a variety of shapes and forms, depending on their makers (ranging from knights in full armor to actual hounds). Meaning that Wirewolves are fucking Chaos Transformers!
When inactive, Wirewolves hang from specially fashioned "gibbets", where arcane practices had made the space thin so that the Immaterium could finger its way through the aether when the correct commands came. They could be summoned by wandering "glyfs" (sentient Chaos runes) at the slightest hint of disturbances from the enslaved population. Once awoken, they were known to be quite uncontrollable, often attacking friends and foes alike.
The downside to the usage of Wirewolves is that they expend their energy quickly, and must periodically return to their "gibbets" to recharge. But when they were fully awoken, there was little that could stand before their assault.
When damaged enough or destroyed, the Wirewolves' ruptured metal carcasses are torn open, unleashing the contained energy in a ferocious explosion that could potentially kill anyone within its blast radius.
Being able to change its form, Wirewolves can make almost any weapon it can forge in a near instant, whether it is razor swords, autocannons or even the simple old fangs. The quick adaptability of the Wirewolf makes it a dangerous and lethal opponent to even Space Marine Sergeants. It is unknown what the Space Wolves would do if they encountered a Wirewolf; they would likely either destroy it or tame it as part of their collection of extra-heretical furry porn. Skyrar's Dark Wolves, on the other hand, likely have an abundance of the monstrosities, because WOLVES.
They are famously known for their encounter with twelve members of the Tanith First and Only's mission on Gereon. Much to the amazement of the Chaos forces, they managed to defeat the Wirewolves that were summoned against them. Most notably, Surgeon Ana Curth destroyed one of the daemonic machines with a number of flasks containing the blessed water from the Balneary Shrine of Herodor (that was originally manufactured by the Departmento Medicae to counteract the effects of Warp-contact on the human metabolism). Suffice to say, the way the Wirewolves was defeated was... quite underwhelming in that regard. All things considered, being killed by something like consecrated silver bolter rounds would make sense since these are, of course, robot werewolves, but holy water? Seriously?