How about some natural armor for DnD 5e?
Casting Time: 1 action
Components: V, S
Duration: 8 hours
You harden your skin and gain a +1 natural armor bonus to armor class. Unless you normally have natural armor, this armor stack with any other armor you wear.
At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, increase the bonus you gain by +1 for each slot level above 1st. If the spell ever gives you a higher bonus than any natural armor you normally, you may use the natural armor from the spell instead of your normal armor.