LUC
Luck (LUC) – increases your success rate while crafting, enchanting, or preventing death. Provides extra loot from spoiling.
While crafting, enchanting or receiving a killing blow, LUC might be applied. When LUC is applied, a clover effect will be visible over the character's head. When this happens a craft or enchant can not fail and a killing blow will have its damage reduced to 0. Although LUC can be applied to a killing blow during an olympiad match, the person receiving the killing blow will lose the match right away and the match will end.
If LUC clover appears during a 
Mug or 
Plunder attack, it means you can mug or plunder the target again for a chance to get the same drop twice.
When using a craft shop, the LUC of the one clicking the Create button is used, not the shop owner.