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Sargeras and the Beytral
To combat the demonic entities that made their way into the Titans' worlds from the Twisting Nether, the Pantheon elected their greatest warrior, Sargeras, to act as their first line of defense. Sargeras, a noble giant of molten bronze, carried out his duties for countless millennia, seeking out and destroying the demons wherever he could find them. Over the eons, Sargeras encountered two powerful demonic races, both of which were bent on gaining power and dominance over the physical universe.
The Eredar, an insidious race of devilish sorcerers, used their warlock magics to enslave a number of worlds that they had invaded. The indigenous races of those worlds were mutated by the Eredar's chaotic powers and turned into demons themselves. Though Sargeras' nearly limitless powers were more than enough to defeat the vile Eredar, he was greatly troubled by the creatures' corruption and all-consuming evil. Unable to fathom such depravity and spite, the great Titan slipped into a brooding depression. Despite his growing unease, Sargeras sought to rid the universe of the warlocks for all time, by trapping them within a vacuous corner of the Twisting Nether.