Braxatskin

Your skin hardens into chitin plates that grant you natural protection, and spikes grow on your body, emerging from your skin with a burst of pain.

You get a +5 enhancement bonus to natural armor, but you suffer a -2 penalty to Dexterity and an additional 20% chance of arcane spell failure. The spikes act as +5 armor spikes, and you gain proficiency with them. You also gain damage reduction 10/metal.