Bark Growth

You imbue a piece of bark in your hand with natural energy, nourishing it. It instantaneously grows to form a thick wooden shield. Gain +5 AC until hit with an attack or spell that would surpass your unmodified AC, or until you cast a spell or use the attack action. When hit with such an attack or taking the actions listed, the shield breaks and prevents you from taking the damage it blocked. 

If hit with an attack or spell that deal fire damage, they pass through the added protection the spell gives as if it wasn't cast, and the shield breaks.