Eldritch Lich

From beyond the stars, a Great Old One whispers promises of reality-defying knowledge and world-bending power. When a wizard or a warlock hears that whisper and listens too intently, they might set foot on the twisting path toward becoming an eldritch lich.
Like other liches, eldritch liches are spellcasters who have cheated death, but an eldritch lich does so by allowing a Great Old One to implant a Far Realm parasite in the lich. That parasite bestows undeath upon the spellcaster and causes strange tentacles to sprout from the body. The parasite’s mouth is visible on the lich’s torso, and the parasite guards the lich against destruction, reviving the lich a few days after death. Canny foes can sabotage an eldritch lich’s revival by slaying the lich in a magic circle, thereby forcing the lich to return in a distorted form, robbed of most of its power.
An eldritch lich constantly hears bizarre whispers from the Far Realm, to which the lich nods and mutters. Occasionally, the lich uses its telepathy to share those whispers with the minds around it.