Thrax

Thrax, the Fleshcrafter, Bane of the Astral Wolves, Prince of Recurrence. Thrax has the dubious honour of being one of only two Daemon Princes to be directly mentioned in the preface to the Black Chapter's notorious Book of the Despised.
The real name of this loathsome daemonic entity is unknown, but he is referred to as Thrax, the name of the Inquisitor whose body was the last that he was known to have possessed.

Inquisitor Thrax had recently completed the purging of the officer core of the Astral Wolves, a previously loyal chapter of the Adeptus Astartes that had fallen to daemonic corruption, when he carelessly allowed himself to become possessed by the very daemon he had just banished.

Unusually this daemon does not seem bound by the ‘thousand years and a day' rule that governs the re-manifestation of his kind, nor the usual time constraint on remoulding the flesh of the possessed. His gaze loosens the bonds between skin and bone, whilst his touch re-knits the flesh into new and chaotic forms. Thankfully for mortals, whatever dark and potent secrets Thrax has discovered, he seems unwilling to share them with his daemonic kin. Indeed, there is no evidence to suggest he is aligned with any of the greater Chaos powers.