Undying of Monvesia

In some settings, the undead are the creation of bored, evil gods who seek to terrorize the mortal world.  In Monvesia, they are a natural offshoot of the transitive region of the Necrosphere.  This region goes by several names:  the Plane of Shadow, the Plane of Fear, the Domains of Dread, the Nightmare Realm.  All undead are powered by this place, and it is in this place that the most powerful of their kind have come to live eternally and rule over their fellows.  These are the Undying who make pacts with warlocks.