Nature's Armor

Prerequisite: Warlock Level 2+, Old Wood patron

You can use your action to sprout hard thorns across your skin for 1 hour. Your Armor Class becomes 12 + your Dexterity modifier, and, when a creature hits you with a melee weapon attack while within 5 feet of you, it takes piercing damage equal to half your warlock level. You must finish a short or long rest before you can use this invocation again.