Legend Lore: Atropus, the World Born Dead

The sages who knew of Atropus all agreed that it was created when Ao created the first gods, though they didn't have a unified theory about how it was born. Some claimed Atropus was the rotting amniotic fluid of the first god of death, while others believed he was a divine mistake by Ao—the last god created, stillborn, immortal and dead upon creation.
Sages saw it for the first time in the ring of the planet Glyth. Atropus was attracted to the planet by the widespread death and destruction the Mind Flayers wrought on the other beings of their world. Atropus laid waste to the planet, leaving it dead and devastated.
Some of the few sages who knew about Atropus believed that its attention was turning toward the Material Plane next, beginning its slow slide to the life-rich planet. They were ever vigilant for signs of its approach—a strengthening of necromancy and the spontaneous rise of the undead.