Fire Snake

The damage dealt increases to 1d10 points of damage per level (maximum 15d10). Any creature that fails its saving throw against the spell is grappled by a snake made of fire that lasts for 1 round per caster level. The snake can be dispelled, but not attacked. A grappled creature takes 1d10 points of fire damage on your turn each round. The snake's CMB is equal to your caster level plus your tier, and its CMD is equal to its CMB + 10.

Augmented (6th): If you expend two uses of mythic power, the maximum damage increases to 20d10, and any creature that fails its saving throw against the spell is pinned instead of grappled.