Gryffindor

There are three Unforgivable Curses. The use of any of them on a fellow human earns the cater a life sentence in Azkaban. Technically, you shouldn't see what these curses look like until your sixth year.
The Cruciatus Curse is used for torture. Bellatrix Lestrange used it on Frank and Alice Longbottom, torturing them into madness. It produces a feeling of pain, unbearable pain. Victims will usually be writhing on the ground.
The Imperius Curse can be used to force someone to do your will. The caster has complete control over the victim. Most commonly, the victim, when the curse is removed, will...