Cairn Form [one-action] Spell 4

Your target's skin becomes a thick carapace of solid stone, granting resistance 5 to physical damage, except adamantine. The target gains a fist unarmed attack that deals 2d6 bludgeoning damage. The target uses their highest weapon or unarmed attack proficiency with these attacks, and if they have weapon specialization or greater weapon specialization, they add this damage as well. On a critical hit with one of these unarmed attacks, the creature struck must succeed at a Fortitude save against the target's class DC or become stunned 1 for 1 round.