The Cruciatus Curse inflicts severe physical pain on the target, usually causing them to scream in agony.
Being one of the three Unforgivable Curses, using it against a human being is punishable by a life sentence in Azkaban.
The spell Crucio is presumed to be from the Latin "I torture".
This spell was first introduced by Mad-Eye Moody
in the Goblet of Fire
, who casted it on an enlarged spider to demonstrate the effects. It has been seen in the later books and movies. Neville Longbottom
's parents were tortured using this spell by a group of Death Eaters, including Bellatrix Lestrange
and Barty Crouch Jr
, which causes the pair of them to be driven into insanity. Neville
felt the affects of this spell when Bellatrix
cast it on him during the battle at the Department of Mysteries