Adamantine Spirit (5e Feat)
From D&D Wiki
Prerequisites: Constitution 13 or higher
With great fortitude of body and experience in battle, you have learned to emulate adamantine both offensively and defensively. You gain the following benefits:
- Weapons you wield are treated as adamantine. Your unarmed strikes are similarly treated as adamantine weapons.
- When an attack roll made against you would score a critical hit, you may use your reaction to negate the critical hit, causing the attack to instead be treated as a normal hit. Once you use this ability you must finish a long rest before using it again.