Sargeras

Sargeras is the creator and leader of the Burning Legion. Once one of the finest champions of the Pantheon, he was selected by his brothers and sisters among the Titan order to defend the worlds the titans had created. Eventually falling to the corruption that the demonic races radiated from within their very hearts and souls, Sargeras went mad before rallying the demons under his banner, the banner of the Burning Legion. Now the titan's worst enemy, he has moved from world to world destroying all semblance of order and balance on each one, effectively undoing the work of his former brothers and sisters permanently. Out of the countless worlds and races he has destroyed only one planet has managed to resist him and his Legion, that planet being Azeroth. Four times the Legion has attempted to invade and destroy all life on the planet and four times they have been beaten back by the native forces of Azeroth losing much of their own in the process.

Currently rumored to be somewhere within the Twisting Nether, Sargeras and his commanders likely plot the next invasion of Azeroth while seeing to their constant war with his former brethren.