Stun

Stun is a curse spell that becomes available at level 80 Magic. If cast succesfully, Stun lowers your opponent's attack by 10%. Stun costs 12 earth-runes, 12 water-runes, and 1 soul-rune.

Trivia

 * Stun, along with Charge, hold the record for the highest Magic requirement in RuneScape Classic