Cruciatus Curse

"Pain. You don't need thumbscrews or knives to torture someone if you can perform the Cruciatus Curse.... That one was very popular once too."

- Barty Crouch, Jr. as Alastor Moody

The Cruciatus Curse is one of the three Unforgivable Curses of the wizarding world. It is a curse of torture, inflicting excruciating pain on a victim. This makes it popular among the Death Eaters for use on both fellow wizards and Muggles. Cursing another human being with Cruciatus carries a punishment of a life sentence in Azkaban.

The two most well-known victims of this curse are the former Aurors Alice and Frank Longbottom, who were victimized with the Cruciatus Curse by Death Eater Bellatrix Lestrange.

Effects
The pain caused by Crucio is said to be worse than "one thousand red hot nails, boring into the skin." The pain caused by the Cruciatus Curse can cause permanent mental injury.

To successfully perform this curse, the wizard must posess a desire to cause the victim pain.

Other Known Uses

 * Harry Potter used this curse against Bellatrix Lestrange in 1996, in reaction to the murder of his godfather, Sirius Black. Though the curse gave her a brief moment of terrible pain, it did not cause the excruciating, drawn-out pain it is meant to give. Severus Snape once asserted Harry Potter had neither the nerves nor the skill to perform unforgivable curses, however less than a year later Harry succeeded in cursing Amycus Carrow. His Cruciatus Curse lifted Carrow into the air and crash-landed him into a bookcase.
 * In 1996, then-High Inquisitor Dolores Umbridge attempted to curse Harry Potter, but Hermione Granger interrupted her incantation.
 * In 1997, Draco Malfoy attempted the Cruciatus Curse against Harry Potter, but was interrupted when Harry attacked him with Sectumsempra.
 * In that same year, a Death Eater attempted to curse Ginny Weasley; through the assistance of Felix Felicis, she dodged it.
 * In that same year, Harry Potter attempted to curse Severus Snape. Snape blocked the curse, and cited his superior skills in Occlumency. All Harry managed to get out was the first syllable of the incantation.
 * In 1998, Vincent Crabbe attempted to curse Harry Potter in the Room of Requirement. However, Harry dodged the curse, and its force hit a stone bust of a warlock instead.
 * In that same year, Lord Voldemort attempted to curse Harry Potter, as he believed him to be dead and wished to dishonour his body. His curse produced no effect because the wand Voldemort used, the Elder Wand, refused to attack its master.

Etymology
Crucio takes its name from the Latin for "torture," from which classical term the word "crucify" also comes.