Beast Shape (all)

Source beast shape

Each mythic beast shape spell must be learned individually, and you must know the respective non-mythic beast shape spell to learn its mythic version. You don't have to learn them in order and are not required to know a lower-level mythic beast shape spell before you learn a higher-level one (for example, you can learn mythic beast shape II if you know beast shape II, even if you don't know mythic beast shape I). Each mythic beast shape spell adds the following benefits to its respective non-mythic version.

The spell's bonuses to ability scores increase by 2, the natural armor bonus increases by 1, and the ability score penalties decrease by 2 (minimum penalty of 0). Choose one natural attack type the animal form has, such as bite or claws. The critical multiplier for this attack type increases by 1 (maximum ×4).

Augmented (2nd): If you expend two uses of mythic power, the ability score bonuses increase by an additional 2. During each casting of the spell, a number of times equal to your tier, you can act as if you had the Natural Spell feat for 1 round. For example, if you're 2nd tier, you can use the Natural Spell feat for 2 rounds per casting of mythic beast shape.