*5th-level Biomancy** (*can be replaced with Transmutation)

Casting Time: 1 action
Range: Touch
Components: V, S, M (a hunk of adamantine worth at least 300 gp)
Duration: Concentration, up to 1 hour
Class: Bard, Bender (earth), Cleric, Druid, Paladin, Ranger, Tamer
Sourcebook: Ryoko's Guide to the Yokai Realms

You touch a willing creature, causing blue-green veins of adamantine to thread through its skin, making it tougher than steel and as flexible as silk. For the duration, the target has an Armor Class of 20 if its AC is lower than that, and it has resistance to acid, bludgeoning, piercing, and slashing damage.

At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the minimum AC increases by 1 for each slot level above 5th.