To get the Breach enchantment in Minecraft 1.21, you need to either enchant a Mace at an Enchanting Table or find an already Enchanted Mace as loot with Enchanted Books while exploring Ominous Vaults.

To get the Density Enchantment for the Mace in Minecraft, you must either use an Enchanting Table on a Mace in your inventory or find it as loot through Enchanted Books within Ominous Vaults.