Thorns

Thorns is a very rare armor enchantment in Minecraft 1.21. Thorns turns your armor into a counterattack, giving a chance to reflect damage back at anything that strikes you in melee or with a projectile.

Its opening level already delivers a noticeable boost — 15% chance to deal 1-4 damage to attacker — and it climbs from there to a maximum of level 3 (III) on your chestplate.

Thorns tops out at level 3, shown as III on the chestplate, and the gap between the levels is where the enchantment's character really lives.

Each of its three levels adds a 15% chance to reflect, so Thorns III triggers about 45% of the time, dealing a small 1–4 points of damage when it does. The catch is durability: a triggered Thorns hit costs the armor extra wear, so it eats through pieces faster than other enchantments.

Thorns can be placed on helmet, chestplate, leggings and boots, giving you a handful of choices for where it does the most good depending on how you play.

Thorns has no exclusivity conflicts at all, so you can layer it onto an item alongside every other enchantment that item accepts without having to give anything up.

Thorns can be rolled directly at an enchanting table, where reaching its top level of III on a chestplate generally wants a fully bookshelf-powered table at roughly level 10. Should the table prove stingy with Thorns, you can instead source the book from loot chest and villager trading and anvil it on.

Its selection weight of 1 makes Thorns a very rare roll: it surfaces only now and then on a chestplate, so you may need to re-roll several times or simply trade a villager for the book.