[Not a transmigration story, no System]
Dumbledore had always thought Voldemort was the greatest threat to the wizarding world, until a vampire who had lived for over a thousand years showed up with the deed to Hogwarts.
"A thousand years have passed. The lease on Hogwarts has expired!" Dracula said. "Headmaster, surely you don't want the students to be left homeless?"
"What do you want?" Dumbledore asked gravely.
"Anything entertaining."
"That can be arranged. I think the Defense Against the Dark Arts professorship would be quite entertaining!"
And so Hogwarts gained a professor no one could keep under control.
McGonagall: "Albus, I really don't think Professor Dracula's teaching methods are suitable for the poor children!"
Dumbledore: "There's nothing I can do. No one can fire him."
Draco: "My father is on the board of governors. I'll make him get you fired!"
Lucius slapped Draco on the head. "Mr. Dracula, Draco is just a child. Please, don't fire the board of governors!"
This is the story of a vampire who had lived so long that he could only find amusement in the wizarding world.