Breach

Breach is a rare special enchantment in Minecraft. Breach makes the mace ignore part of a target's armor, so its hits land closer to full damage against well-protected enemies.

Its opening level already delivers a noticeable boost (Ignores 15% of the target's armor), and it climbs from there to a maximum of level 4 (IV) on your mace.

Breach tops out at level 4, shown as IV on the mace, and the gap between the levels is where the enchantment's character really lives.

Each of its four levels reduces the target's effective armor by 15%, so Breach IV ignores 60% of their protection. Against an unarmored target it does nothing extra, but against heavily armored players and mobs it dramatically raises the damage that gets through.

Breach fits exactly one item (the mace), and nothing else will accept it, so it is a dedicated mace enchantment through and through.

Breach cannot share a mace with Sharpness, Smite, Bane of Arthropods and Density. All of these sit in the same mutually-exclusive group as Breach, so a mace can wear only one of them at once and you choose which playstyle to commit to.

Breach can be rolled directly at an enchanting table, where the level you pay and the enchantability of a mace together decide which level of it you can be offered, up to IV. Players who would rather not gamble for Breach can hunt the book down through loot chest and villager trading and apply it at an anvil.

Its selection weight of 2 makes Breach a rare roll: it surfaces only now and then on a mace, so you may need to re-roll several times or simply trade a villager for the book.