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

Surging Blood Magic

FEAT 12

Prerequisites Rising Blood Magic; master in Arcana or Religion, depending on your chosen tradition

Your blood courses with magic. You gain the Expert Spellcasting Feat benefits. In addition, when you Cast a Spell from your repertoire and you are at least Drained 2, increase the extra damage dealt by that spell from Rage by an additional 2 (for a total of 3).

Pathfinder War of ImmortalsORC