Rammfish

"A knot of fury covered in hard growths. Mutation has transformed its skull into a bony fist that neither Anglers nor the aquatic denizens of Bone Reef would ever wish to encounter. Rammfish swiftly builds up speed and slams into its victim, fracturing the skull and bones or knocking the target unconscious. Only then does it begin feasting alongside its kin that have not yet been touched by mutation. There have been cases of Anglers' bodies being found with this horrific fish lodged in their shattered skulls... Its jaws are used to make bait and armor, though less extensively than chitin because they come in much smaller pieces."