The Harbingers of Death, also known colloquially as Bringers, are the priests and foot soldiers for the non-corporeal First Evil. The Bringers are humans who have been corrupted by the First and undergone rituals that include self-mutilation. Though Bringers are blind, with eyelids covered by rune-like scars, and incapable of speech, having their tongues ripped out, they are perfectly aware of their surroundings.
It is implied that the First's high priest, Caleb, has played an important role in indoctrinating the Bringers. He possesses extensive knowledge of their habits (such as knowing that they pant instead of sweat) and refers to them as "my boys". Indeed, The Harbingers of Death themselves refer to him as their "teacher".
The Bringers also have a poisonous aura which is capable of rendering earth and living beings sterile:
"For they are the harbingers of death, nothing shall grow above or below them, no seed shall flower, neither in Man nor..."
Despite their apparent disabilities, Bringers are swift assassins capable of highly organized attacks thanks to their collective consciousness, which is under the control of the First. Besides their deadly fighting skills, Bringers are also capable of summoning manifestations of the First to haunt people, and create psychic links between dreamers through their dark rituals.
In season 7, The First declared war on the Slayer line. The Bringers became assassins of Potential Slayers around the world. When the First set up camp in Sunnydale, Bringers begin to swarm the town to hunt down arriving Potentials and to unearth the Scythe, a mystic weapon created by Guardians, ancient, powerful women who cared for the Slayer.