The Darkness

Hunger: hunger itself.

Prime power: darkness.

Homeworld: Umbra, in which is no light at all—it cannot be perceived or felt in that place, except in small pockets which its Lord may design. 

Those who are of the Darkness hunger. Most eat; some collect. There are those who can and do devour anything, including plague, radiation, and the dead. 

So have many fallen to their appetite, even to devour the magic and flesh of others among the Mythos; the Fey, in particular, are much prized.

Toward the end of their natural lifespan, their own forms can no longer satisfy their aching, empty need. Those who are the most ancient and venerated grow more shadowed, less substantial, and eventually explode into ash.