Warlock Pact Boon 1Dark One's Blessing

You instantly gain vitality from a cursed enemy when that enemy falls.

Free Action      Personal

Prerequisite: Infernal Pact

Trigger: An enemy under your Warlock’s Curse is reduced to 0 hit points or fewer

Effect: You immediately gain temporary hit points equal to your level.

Published in Player's Handbook, page(s) 131.