Zar'Ilmask

Zar'Ilmask are an incorporeal infernal creature who primary operate as a type of parasite on mortal hosts in the material plane. The host-parasite combination are commonly referred to as Warlocks. The infernal creature itself are innately powerful in the realm of mental influence and control, as well as capable of manipulating shadows and illusions to create nightmarish imagery and summoned monsters to act as they choose. In order for them to interact with the material world, they must have a host and cannot survive on Arawyn outside of one.
These creatures live in the Abyss and are ruled over by the Zar'Ilmask council - an organization of the 13 most powerful among them.