From Pathfinder Lost Omens The Grand Bazaar, which isn't enabled.

Bloodthirsty

ITEM 16

Price 8500 gp

Usage etched onto piercing or slashing melee weapon

Bulk —

The magic in this rune sings in time with your attacks and coaxes you into finishing your opponent. When you critically hit a target that's taking persistent bleed damage, your target becomes Drained 1.

Activate envision

Trigger You reduce a creature to 0 Hit Points with the weapon

Effect You gain a number of temporary Hit Points equal to twice the creature's level. These Hit Points remain for 1 minute.

Pathfinder Lost Omens The Grand BazaarOGL