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

Invoke Infernal Flames

FREE ACTION

Activity free action

Trigger You critically hit a creature with an unarmed attack granted by this feat

Requirements You are doomed

Effect You deal an additional die of weapon damage and 1d4 persistent fire damage. Then, increase the value of your doomed condition by 1.

Pathfinder Lost Omens Cheliax, Infernal InheritanceORC