A blackened sun, eclipsed in blood
Figures in robes chant guttural hymns as a man with a curved dagger approaches a bound sacrifice.
The Blackened Sun is a doomsday cult that worships not a specific deity, but rather the concept of entropy and a return to primordial darkness. The cult is said to have arisen within the last few centuries, but adherents claim that their religion traces back to the dark ages following the apocalypse.
It has been discovered that the high priest of the cult is not only a lich, but is also the Fourth, who claims to have led the congregation since its inception in the dark past. The Fourth's devotion to his master is clear; even if the members of the Blackened Sun do not realize to what or whom they are praying, their faith may be strengthening the Necromancer.
Every time authority figures flush out a cult branch, a few worshippers always manage to escape, only to set up similar cults in new regions after years or even decades of lying low.
Legio XIII hired changeling assassins to infiltrate Willowdale in order to weaken the town's spellcasting ranks before the Battle of Willowdale. Each of these assassins bore marks of the Blackened Sun over their hearts. According to the reformed changelings, a grand cathedral dedicated to the Blackened Sun exists in the Western Rainforest beyond the Bone Ziggurat.