pf2e.fyi
From Pathfinder #176: Lost Mammoth Valley, which isn't enabled.

Defensive Needles

FEAT 5
Prerequisites Cactus Leshy or Pine Leshy heritage

Your body is covered in sharp needles or spines which you can use to defend yourself. Each time you become Grabbed by a creature or an adjacent creature hits you with an unarmed attack, you twist and thrash your body around, dealing 2 piercing damage to that creature. This damage increases to 3 at 9th level, 4 at 13th level, and 5 at 17th level.

Leveled damage

Pathfinder #176: Lost Mammoth ValleyOGL