Adamantine Body Technique

You have a bonus to your AC while attuned to this secret technique and not wearing armor. You also get a bonus to your attack and damage rolls with your unarmed attacks. The bonus is determined by it’s rarity.

To attune to them you need to spend time studying the manual or training with the master, usually a cumulative 24 hours of dedicated study. After you've attuned it once you can unattune it at any time and you can reattune over a short rest.