Improved Dark One's Blessing is a heroic tier feat available to warlocks with an infernal pact and an Constitution score of 15 or higher.

Normally, a warlock with an infernal pact gains temporary hit points equal to the warlock's level when an enemy under the warlock's Warlock's Curse is reduced to 0 hit points or fewer. A warlock with the Improved Dark One's Blessing feat gains an additional 3 temporary hit points in this circumstance.[PH:198]