Barkskin

Source: Player's Handbook

2nd-level transmutation

Casting Time: 1 action
Range: Touch
Components: V, S, M (a handful of oak bark)
Duration: Concentration, up to 1 hour

You touch a willing creature. Until the spell ends, the target’s skin has a rough, bark-like appearance, and the target’s AC can’t be less than 16, regardless of what kind of armor it is wearing.

Spell Lists. Druid, Ranger