Character: Karxus

The evil has to have name and face. In our story it’s ancient evil demon who once threatened to take over the world. Armies of different races rose against his hordes. Wizards and mages faced the great demon, but they were not able to destroy him. I haven’t figured out why they couldn’t kill him. They only managed to capture and lock him in a place unknown to any of his surviving followers or servants. He’s the top boss.