Hematophage/Fallout 3

Hematophage is a special perk in Fallout 3.

Effects
This perk allows you to regain significantly more health by consuming blood packs. Blood packs heal 20 hit points, equivalent to a bottle of purified water instead of 1 hit point.

To obtain this perk, convince Vance to enter into a deal with the town of Arefu by passing a Speech check, a Medicine skill check, or an Intelligence check at the conclusion of the Blood Ties quest. Then return to Vance and ask to be shown the ways of the vampire.

Behind the scenes

 * Hematophagy is the habit of certain animals feeding on blood (from the Greek words haima, blood, and phagein - to eat).