Breach

Breach is an enchantment applied to maces that causes melee attacks to partially ignore armor, increasing damage against armored targets. It also affects the natural armor points that certain mobs have innately.

Breach can be obtained through an enchanting table by enchanting a mace or a book, or by trading with a librarian of any level​[until: Villager Trade Rebalance], or from fishing. Its enchanted book form can also be found from ominous vaults, as well as any other structures that generate enchanted books.

Breach reduces the effectiveness of the target's armor points and armor toughness by 15% per level. Specifically, Breach deals damage as though the enemy's damage reduction from armor was 15 percentage points lower per level. For example, if the enemy's armor reduces damage by 50%, and they are hit with a mace with Breach I, their armor reduces the damage by 50% - 15% = 35%. However, this reduces the effectiveness of only the armor itself, which does not include damage reduction from enchantments such as Protection or the Resistance effect.