Well, I have two old and cruel characters, namely in the form of Chenaank, the Demon God of Wealth and Greed, and Kruz'Iik.
Chenaank definitely fits the bill of cruel, old, and ruthless. Kruz'Iik is definitely ruthless and old, but he's not as cruel as Chenaank. Although, he's still capable of pretty ruthless acts of violence. He's particularly good at torturing people mentally, so that could be a thing.