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

Faultless Defense

FEAT 14

Activity reaction

Trigger You would take damage from a Strike made by a creature.

As you are struck, your steely determination reminds those who fight you that they are destined to be no more than footnotes in your tale. Spend a Mythic Point to gain resistance equal to half your level to the triggering damage, and then attempt a Strike at mythic proficiency against the creature that attacked you. If the Strike hits and deals damage, the creature is also Slowed 1.

Pathfinder War of ImmortalsORC