Time-Turner

When Time-Turner enters, you get {H}{H){H} (three House point counters).
Whenever you learn or cast a Lesson,
you get {H}{H}.
Lose seven {H}, Exile Time-Turner: Take an extra turn after this one.

"I got it from Professor McGonagall on our first day back. She had to tell them that I was a model student, and that I'd never, ever use it for anything except my studies..."