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
This perk can be obtained by convincing 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, by returning to Vance and asking 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)).