The Harbingers are a covenant of vampire death mages who have learned to stave off torpor.
According to the Harbingers, vampires are not undead, but rather dying very, very slowly. They describe torpor as the result of too much accumulated "death energy" or "Necrosis" in the soul. During torpor, however, the soul travels to the Underworld and drains the excess Necrosis. Their signature Discipline, Thanatology, allows the Harbingers to manipulate Necrosis without going into torpor--either absorbing more of it and thus making themselves more powerful (modeled in game as an increase in Blood Potency) or, more often, draining off some of it so that they can remain active indefinitely.
This Discipline only functions in areas already suffused with a certain amount of Necrosis--graveyards, funeral parlors, the site of a mass murder. Cultivating an appropriately morbid atmosphere (a practice called "gravetending") helps. But Necrosis cannot simply be drained away--it has to go somewhere. The best receptacle is another vampire, but in a pinch a ghoul will work, or any being touched by Death (a Promethean, a Sin-Eater, a Moros mage, etc.). Many Harbingers quietly kidnap elders from other covenants in torpor and use them as Necrosis sinks--the victim never awakens, as their blood never thins sufficiently.
The same locations that make a suitable site for Thanatological rituals also tend to attract other users, whether it's werewolves attempting to tend a Wound or members of the Ordo Dracul seeking out a Wyrm's Nest. Thus it is not unusal for Harbingers to get into a territory scrap over a particularly useful ritual site.
This is a relatively young covenant, but it has proven quite attractive to elders, especially those who have already been through one torpor and want to avoid another. Ancillae Harbingers are less common, and neonates effectively non-existent--it is difficult to care about torpor when it's still so far off. Still, those Embraced by a Harbinger are expected to join the covenant one day, and encouraged to divest themselves of any attachments to the mortal world as quickly as possible. Harbingers as a rule do not interact with the living except to feed; they spend most of their time gravetending, or guarding the local Necrosis sinks.
Carthian Movement · Circle of the Crone · Invictus · Lancea Sanctum · Ordo Dracul