Hematophage

Hematophage is a Fallout 3 special perk. It can only be gained through the Blood Ties quest.

Blood packs heal 20 Hit Points instead of only 1.

Obtaining the perk
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 practice found in certain animals of feeding on blood (from the Greek words, αίμα (blood) and φαγειν (to eat)).