Goyg

Mutating parasite creatures that feed and grow rapidly on the dead. Goygs become gargantuan monsters in the battlefields of dead bodies they emerge out of. The more carion they feed on the larger they grow. 
Goygs are extremely dangerous. The rapid growth of a goyg can finish off a victor in the field of war, and is a death knell to armies. 
Goygs have physical characteristics similar to a Lhurgoyf in Magic the Gathering. 
Also: Necrogoyg or Mordigoyg