Throll

Known only as Throll, the Dragonborn warlock had an unknown Patron and was incredibly secretive about who he chose to serve.
Coming from a background of servitude, it is assumed that Throll grew tired of being mistreated, even though he was supposedly one of the Children of Gods and desired to forge a new place for himself and those treated as servants.
After years of generating dissent at his masters, he broke out, inspiring waves of the 'Shadestained' races to join up with his cause, promising power and land to all those that stood with him.
After his death in The Culling, his name is used as a profanity the land over, whispered only in hushed discussion by those who wish his campaign had succeeded.