High Crit

A high crit weapon deals more damage when you score a critical hit with it. On a critical hit, the weapon deals 1[W] extra damage at 1st–10th levels, 2[W] extra damage at 11th–20th levels, and 3[W] extra damage at 21st–30th levels. This extra damage is in addition to any critical damage the weapon supplies if it is a magic weapon.

Published in Player's Handbook, page(s) 217, Mordenkainen's Magnificent Emporium, page(s) 20, Rules Compendium, page(s) 269.