Oakenhide 2014

You magically encase your body in a hard shell of bark. You gain 6 temporary hit points at the start of each of your turns, and while you have these temporary hit points, you can calculate your AC as 15 + your Dexterity modifier (maximum of +2).

When you cast this spell using a spell slot of 3rd level or higher, your AC increases by 1 for every two slot levels above 2nd. The temporary hit points increase by 3 for each slot level above 2nd.