Hunger

The Hunger is the demon half of a White Court vampire.

Description
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 born with the Hunger but 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 House Malvora and House Skavis 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 if 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.

After the Hunger has fully manifested, coming into contact with emotions antithetical to that which the vampire feeds upon will inflict severe burns upon the host vampire, such as if a Raith vampire touched a wedding ring; the symbol of love being antithetical to lust. However, Thomas Raith explains that getting burned when trying to feed on someone in true love is not a simple matter. The severity of the burns has to do with how much control the Hunger has over the White Court House Raith vampire when they touch.

White Court vampires can cross a threshold but it cripples their ability to draw on their Hunger for strength and speed.

Grave Peril
In Grave Peril, Harry Dresden finds it interesting how Thomas Raith can subdue The Nightmare by feeding off of Lydia, whom The Nightmare was possessing. Harry muses about whether the Hunger was "some kind of ambient magic" that affects all nearby entities, or "something chemical—like Red Court venom. Something that got to Lydia’s body and bypassed the Nightmare’s control of her mind, altogether." Harry describes the Hunger feeding off of Lydia thusly: "I felt cold coming off [of Thomas], something I sensed more than felt on my skin, a horrible and seductive cold."

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

Backup
In Backup, Thomas Raith's Hunger finally manages to feed properly on the Stygian he's been confronting.

Turn Coat
In Turn Coat, Thomas Raith explains that when he's with Justine who means a lot to him, everything in him wants to be near her including his demon. He can't touch her without it being close to the surface. So, it burns him. The difference with Madeline Raith is that the Hunger controls her completely, she thinks she gets to feed on everyone and just sees food. For both of them it's a reflex.

Ghost Story
In Ghost Story, Felicia crosses the threshold of Karrin Murphy's home without an invitation. According to Harry Dresden, this action is gutsy because it cripples the White's ability to draw on their Hunger for strength and speed.