Thorns

Thorns is an armor enchantment that causes attackers to be damaged when they deal damage to the wearer.

Guardians and elder guardians have a Thorns-like effect which inflicts damage when their spikes are out. However, this only affects melee damage, whereas the enchantment applies to all direct attacks, including ranged.

Usage
While wearing any piece of armor with the Thorns enchantment, the wearer has a  chance of inflicting – damage on anyone who attacks them, regardless of whether they were hit by a melee attack, arrow, or other projectile. The entity also gets knocked back when being attacked by the enchantment.

Multiple worn armor items with the Thorns enchantment do stack. Each piece confers an independent chance to deal damage to the attacker as described above. The total amount of damage that can be dealt this way is capped at.

Probabilities of inflicting maximum damage and average damage dealt depending on the number of items with Thorns III worn are as follows: Thorns applies a durability penalty to the armor. It reduces durability by an additional 2 points when inflicting damage. If multiple armor pieces are enchanted with Thorns, the durability penalty is applied to one piece chosen at random, regardless of what level of Thorns that piece has. If the item is also enchanted with Unbreaking, the damage penalty has a chance of being ignored.

If a projectile is launched toward an opponent equipped with thorns, using a shield damages the shield instead of the player when the projectile hits the opponent.

Using commands, the enchantment level can be increased. The maximum possible chance of dealing damage is 100% (at level 7). If the level of Thorns exceeds 10, then it deals  damage.

$$ although horse armor cannot be enchanted in Survival, the Thorns enchantment can be applied to horse armor in Creative and it works.

Obtaining
Thorns I and II can be applied to a chestplate through normal enchanting, but not Thorns III. Thorns can't be applied to any other piece of armor (helmet/leggings/boots) using an enchanting table, but you can use an anvil to apply it to all armor. Thorns I and II can be obtained naturally from drops, fishing, trading with a villager or as loot from generated structures.

Thorns III cannot be directly obtained using an enchanting table, but it can be obtained by using an anvil to combine two Thorns II enchantments, by trading with villagers, or by finding an item enchanted with it from the loot chest as below.

The enchanted book with Thorns III can be found within the following structures:

Underground structures


 * Mineshaft
 * Stronghold

Underwater structures


 * Ocean Ruins

Aboveground structures


 * Desert Pyramid
 * Jungle Pyramid or Jungle Temple
 * Pillager Outpost
 * Woodland Mansion

Miscellaneous structures


 * Dungeon

Pieces of armor enchanted with Thorns III can be found within the following structures:

Underwater structures


 * Shipwreck

Small structures


 * Ruined Portal

The Nether


 * Bastion Remnant


 * Ruined Portal

The End


 * End City

Thorns can be applied to a non-armor item only by using creative mode, commands or a third-party tool. When such an item is held in either hand, an attacker suffers damage according to the formula above.

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