Urchin

You flex the spines running down the back of your head and neck as a defensive response. The attacking creature takes 3d6 piercing damage, with a basic Reflex save against your class DC or spell DC, whichever is higher. On a critical failure, the target also takes 3 persistent bleed damage. At 8th level and every 3 levels thereafter, the damage increases by 1d6, and the persistent bleed damage increases by 1.