Quest ransack

Quest Ransack, as introduced in Update 19, is a stacking penalty for repeatedly playing the same quest. You may play each difficulty level once per character, per incarnation without incurring Quest Ransack penalties. After that, each playthrough will add a 20% stacking penalty to base XP, up to a maximum of -80%. 18 hours after the most-recent completion the penalty is reduced by 50% (and again 18 hours after that). This 18 hour timer restarts each time you run a quest, so if you never leave a full 18 hour break between runs of the quest you will never get any reduction in the 80% penalty, and if you never wait a full 36 hours you will always have some penalty.

See also:
 * Experience bonuses and penalties in quests
 * Lamannia forum official thread
 * Update 19 Release Notes