You have learned to make your summons destructive to the fabric of the planes, bringing blackfire in the wake of your magic.
Prerequisite(s): Sacred Summons.
Benefit(s): When you summon a single evil outsider, it appears in a flash of blackfire, harming all adjacent nonevil creatures. This deals an amount of damage equal to twice the CR of the summoned creature. An affected creature can attempt a Will save (DC = the DC of the spell used to summon the creature) to halve this damage. A spell augmented with blackfire summoning uses up a spell slot 1 level higher than the spell’s actual level. If you have the blackfire pact class feature, you can apply the benefits of this feat to summoned outsiders of the type or types you have selected for your blackfire pact without raising the spell’s effective level.
Pathfinder Player Companion: Plane-Hopper’s Handbook © 2018, Paizo Inc.; Authors: James Case, John Compton, Leo Glass, Avi Kool, Adrian Ng, Lacy Pellazar, Daniel Reed, Mikhail Rekun, Amber E. Scott, Tork Shaw, and Linda Zayas-Palmer.