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Imperius Curse- One of the three unforgivable curses. This curse is illegal and its use can be punishable by sentence to Azkaban and/or dementor's kiss. The imperius curse allows to the caster to control the mind of the subject. However, the curse can be broken if the subject is strong minded and normally talented in Occlumency.

Inquisitorial Squad- A small group of students who helped professor Umbridge watch for misbehaving students. It was made up of mostly Slytherin students. Members were Vincent Crabbe, Gregory Goyle, Daphne Greengrass, Draco Malfoy, Graham Montague, Pansy Parkinson, Millicent Bulstrode, C. Warrington, and an unnamed sixth year girl.

International Confederation of Wizards- Wizarding intergovernmental cooperation similar to that of the United Nations.

Invisibility Cloak- Cloak of Invisibility. Two are known. One belonging to Barty Crouch Sr. and the other to Harry Potter, formaly James Potter. When worn, the cloak turns the person invisible to the eye. The Invisibility Cloak (Harry Potter's at least) is one third of the Deathly Hallows.