Your headbutt is delivered good and hard. Don’t mind the headaches.
Prerequisite: Thick Skull.
Benefit: You can choose to increase the damage of your headbutt natural attack by +2d4, +4d4, or +6d4. For every 2d4 you increase your damage by, you take 1d4 damage. You must increase the damage by 2d4 increments, so you could not increase the damage by 1d4, 3d4, or 5d4.