Arboreal Hammer

Source arboreal hammer

You animate two branches instead of one, allowing the tree to attack twice per round. Add your tier to your caster level when determining the tree's Strength score. A creature struck by both slam attacks in the same round must succeed at a Fortitude save against the spell's DC or be staggered for 1 round.

Augmented (7th): If you expend two uses of mythic power, the tree attempts three slam attacks per round and its slams bypass all damage reduction. A creature struck by all three slam attacks in the same round is stunned for 1 round and staggered for 1d4 rounds after the stun ends. A successful Fortitude save negates the stun and reduces the duration of being staggered by half.