One of the three Unforgivable Curses; the Cruciatus curse causes agonising pain
Crucio fact file
To inflict excruciating pain on the recipient/victim
It was pain beyond anything Harry had ever experienced; his very bones were on fire; his head was surely splitting along his scar…he wanted it to end … to black out … to die.
The spider’s legs bent in upon its body; it rolled over and began to twitch horribly, rocking from side to side.
You need to mean them, Potter! You need to really want to cause pain – to enjoy it - righteous anger won’t hurt me for long
Harry Potter and the Order of the Phoenix
By J.K. Rowling
And then Harry heard Krum’s voice.
The air was suddenly full of Cedric’s yells.
Harry Potter and the Goblet of Fire
by J.K. Rowling