Kristoff is an old pirate from the 1600’s. He was captured and hung, but you know hanging doesn’t work on the undead. He got himself free and killed most of the witnesses(the ones who didn’t run away). After the Golden Age of Piracy ended, he went into hiding, later using his accumulated wealth to appear as a nobleman.

Of course, the appearance took all of his wealth, and he turned to getting money off of people by promising them immortality to keep his bills paid and his nice clothes to cover his old tattoos. Generally, he would just lift the money off of them and then kill them, though from time to time, if his whims went the right way, he would turn them.