Caustic Blast

You fling a large glob of acid that immediately detonates, spraying nearby creatures. Creatures in the area take 1d8 acid damage with a basic Reflex save; on a critical failure, the creature also takes @Damage[(1+floor((@item.rank -1)/2))[persistent,acid]] damage.

Heightened (+2) The initial damage increases by 1d8, and the persistent damage on a critical failure increases by 1.