The Hollow are an Extempore Promethean Lineage. Creatures of drought and deprivation, they are possessed of a perpetual hunger that only the New Dawn can fulfill. They were given life by the elements of earth and air, and they suffer from excesses of melancholic and sanguine humours.
The Hollow could only be created, and reach the New Dawn, during the Dust Bowl of the 1930s American Midwest. After it ended, no new Hollow could be created, meaning that those Hollows who had not already created progeny could not complete their Pilgrimage. When the rains finally came, some Hollows were ready, finally becoming human, and some died, their Divine Fire snuffed out. Most of the survivors left the USA in the hope that they could complete their Pilgrimages elsewhere, in places as desolate and deprived as the Dust Bowl.
The Hollow creation rite requires the corpse of someone who died of deprivation, be it physical deprivation, such as hunger or thirst, or spiritual deprivation, like despair. The creator must then make the corpse even emptier than before in some way, then anoint its brow, hands, and chest with a handful of dust. Once that's done, the creator must place a spark of their Pyros into a drop of water and place it on the corpse's lips, awakening it as a Hollow.
As hungry, angry creatures, Hollows tend to default to Stannum. A Hollow who feels secure, whose needs are satisfied, might follow any Refinement, although they generally go with Aurum, Cuprum and Ferrum, Refinements that offer some immediate benefit for security; other Refinements are too abstract to keep their attention long.
The Hollow are defined by hunger, by their awareness of an emptiness within they need to fill, which drives them to seek security, comfort, and satisfaction, to become human. Some distract themselves from their true hunger with food, alcohol, drugs, and even sex, but only the Pilgrimage can really sate the hunger for any length of time.
The Hollow Bestowment Hunger (subsequently renamed Bloody Feast) lets them put their constant hunger to good use, absorbing damage from an attack on or around them and converting it into Pyros and/or strength of will in any combination. However, the damage is only delayed for a while, not denied, resulting in them eventually suffering all damage accumulated. Their other Bestowment, Vice Eater, allows them to infect others with their hunger to strengthen their desires, impairing their judgement.
In human form, a Hollow will bear some sign of their hunger - chapped lips, emaciated body, a too-intense gaze. When their disfigurements appear, they become inhumanly gaunt, their skin pale or ashy, their eyes so bloodshot they appear to glow red. Their flesh is dry and flaky, drawing back from their bones, sometimes even ripping so viewers can see through the gaps between their ribs. However, they rarely smell in Promethean form, as their bodies are too desiccated.
The Hollow's second edition summary in Night Horrors: The Tormented changes the Hunger Bestowment's name to Bloody Feast, introduces the Vice Eater Bestowment, and opens up the possibility of fulfilling the multiplicatio requirement of the Pilgrimage without creating progeny.