The Imperius Curse is a fictional spell from the Harry Potter Universe
The Imperius Curse is one of the three Unforgivable Curses, and as a result, people found to have cast it sufer harsh punishments. The Imperius Curse grants the caster the ability to control whoever the spell is cast at, and bend their will to force them to commit desired acts. It is often used by Death Eaters to force people who are generally on the right side of the law to make them commit the crime and take the blame, much like Stan Shunpike, who is forced to help the Death Eaters.
The incantation for the Imperius Curse is Imperio.