From Pathfinder Lost Omens Cheliax, Infernal Inheritance, which isn't enabled.

Shadow's Assault

FEAT 13

Your shadow assaults your foes. You can cast Shadow Blast as a 5th-rank occult innate spell once per day. At 17th level, your shadow blast is heightened to 6th level.

Pathfinder Lost Omens Cheliax, Infernal InheritanceORC