Necroblight

Grotesque parasites, these creatures corrupt the nature of death, and undeath, itself. When a humanoid with a strong Primal aura about it is raised as an undead, these parasites unerringly find their way to it and imbue the undead creature with the additional power of Blight. Commonly they break away from the control of the necromancer who raised them and follow the unknowable purpose of Blight, trying to corrupt other natural creatures.
Necroblights look like other types of undead such as skeletons or zombies, but with sickly vines or patches of moss growing out of them.