By the Emperor! This thing is HUGE!
If you remember, the Nurgle Daemonhost was one of our earliest concept arts, now you can see it in its full 3D glory. Zoom in, rotate as you please, as it has appeared on Sketchfab:
This entity is warped beyond recognition by a corrupting Nurgle Daemon: its twisted form resembles nothing amicable or orderly, so naturally its main purpose is to be purged by the Inquisition.
However, this one is a formidable foe: a gigantic boss-like creature with numerous strong tentacles... it would take a bit more cunning and brute force to take it down.
Be prepared, as this fellow will eventually block your path towards glory... and it will be a true test of faith and courage for Inquisitors!