Professor Moody uses the Cruciatus Curse on a spider in his Defence Against the Dark Arts class. Under the influence of the Cruciatus Curse, the spider's legs bend in upon its body; it rolls over and begins to twitch horribly, rocking from side to side. No sound comes from the spider, but Harry is certain it would be screaming if it could. The longer the Curse is performed on it, the harder the spider shudders and jerks. The Cruciatus Curse was a very popular curse at one time.