From Pathfinder Lost Omens Knights of Lastwall, which isn't enabled.

Chemical Purification

FEAT 4

Activity free action

Frequency once per round

Trigger You use Quick Alchemy to craft an alchemist's fire or ghost charge, and that bomb's level is at least 2 levels lower than your advanced alchemy level.

You developed a method to chemically purify and consecrate your bombs on the fly. You include this additive mixture when crafting your alchemist's fire or ghost charge. The created bomb deals 1d4 persistent vitality damage in addition to whatever damage it would normally cause. As usual for vitality damage, this damage harms only undead and creatures with void healing.

Pathfinder Lost Omens Knights of LastwallOGL