pf2e.fyi
From Pathfinder War of Immortals, which isn't enabled.

Mythic Casting

FEAT 10
Activity 1 action

You can infuse mythic power directly into your spells to make them exceptionally potent. Spend a Mythic Point; if the next action you use is to Cast a Spell, use mythic proficiency to determine your spell attack rolls and save DC for that spell.


Note: PFS 6-09 allows for the action you use next to be a kineticist impulse, using your mythic proficiency instead of impulse attack rolls and save DC.

Pathfinder War of ImmortalsORC