Carcass Crab

Presumably once mundane crabs, but twisted and mutated by the Mourning, a carcass crab is a huge crab coated in venomous spines and an adhesive substance. They cover themselves with dead bodies, discarded weapons and armour, and other detritus found on a battlefield, further armouring their already thick shells. This covering also allows the crabs to camouflage themselves amongst the many battlefields spread across the Mournland.
Whilst they are primarily found in the Mournland, and have only been seen since the Day of Mourning, they haven't all stayed in the Mournland, and sightings have been confirmed in both Darguun and Valenar.