Hunger

The Hunger is the demon half of a White Court vampire. While this demon can grant the vampire incredible strength and durability, its gifts come with a price: the need to feed on the life energy of mortals. If the vampire does not feed its Hunger, he will become increasingly weak and may die.

White Court vampires are not born with the Hunger; it only begins to manifest as they reach maturity, and will become fully a part of them after their first - and always fatal - feeding. It is unknown whether all houses of the White Court first manifest their Hunger during sex, like House Raith, or if Malvora and Scavis first manifest in other ways.

If a Raith vampire has sex for the first time with someone he or she truly loves, the Hunger will die and the vampire will be free of it forever. They will also lose their supernatural prowess, including immortality. It is unknown of vampires from the other White Court houses can kill their hunger in a similar fashion, feeding on someone with whom they share the emotion that is the bane of their house.

When Harry shares a soulgaze with Thomas, he is able to see the vampire's Hunger as a monstrous entity with whom Thomas is in a constant strugle; Thomas is fighting to maintain a measure of humanity and control, and his Hunger wants him to be a ravening predator.