The Exocrine is one of the most feared gun-beasts in the Tyranid arsenal, a heavy organism bred to deliver long-range devastation. Mounted upon its broad back is a monstrous bio-plasmic cannon, and from this weapon the creature looses either a single vast sphere of superheated plasma or several focused streams from its cluster of barrels, each capable of reducing armour and infantry alike to ash.
What unsettles those who study the Exocrine is the relationship between beast and weapon. The great cannon is no mere tool grown onto a host; it is a symbiote with a brain of its own, and it is that brain, not the lumbering body beneath it, that governs the creature. Imperial observers have concluded, with some disquiet, that the weapon is the more intelligent of the two, the vast body serving as little more than a means to carry its parasitic master to a good firing position.
The symbiote does its deadliest work when the Exocrine stands still, for only then can it pour the whole of its considerable focus into acquiring and annihilating targets. Yet the beast is no helpless artillery piece; should an enemy close the distance, the Exocrine can rise up and crush or gore them with raw physical power, a reminder that even the swarm's gunners are monsters first.