Malstrain Alpha

Rumours of the Malstrain Alpha have persisted for as long as explorers have braved the Underhells of Hive Secundus, and the running theory is that it is a direct descendent of the original Patriarch.
Few have ever seen the creature and lived to tell the tale. Despite its twisted appearance, it is a consummate hunter who views anything entering its domain as prey. It effortlessly stalks them as its unique biology allows it to morph and contort, slipping through too-small gaps to pursue its quarry and bursting out from vents to eviscerate its opponents.
It carries within it the Madness of the Malstrain, and anyone who attempts to face off against this monstrosity risks having their very psyche shattered.