The Blood Professor at Hogwarts

Originally titled "Professor Vampire Earl of Hogwarts"——
[Non-time travel text, no system]
Dumbledore always thought that Voldemort was the greatest threat to the wizarding world, until a vampire who had lived for more than 1000 years came to him with the title deed of Hogwarts——
"The millennium has passed, and the lease of Hogwarts is up!" Dracula said, "Mr. Principal, you don't want the students to be displaced, do you?"
"What do you want?" Dumbledore asked solemnly.
"Anything interesting."
"It's easy to handle, I think the position of Professor of Defense Against the Dark Arts is very interesting!"
……
As a result, Hogwarts had an extra professor who was left alone.
McGonagall: "Albus, I don't think Professor Dracula's teaching is suitable for poor children!"
Dumbledore: "I can't help it, no one can fire him."
……
Draco: "My dad is the school trustee, I will definitely let him expel you!"
Lucius slapped Draco on the head, "Mr. Dracula, Draco speaks like a child, don't dismiss the school board!"
……
It's the story of a vampire who's lived so long that he's bored enough to find fun in the wizarding world.