A being manifested from all evil in existence, the First is an incorporeal entity that can assume the appearance of any person who has died (however briefly) – including vampires and humans who have been resurrected.
It can take the form of anyone who has died (or as an enormous, phantasmic demon with large horns and long, talon-shaped fingers), and it can choose to be seen and heard by just one person or by multiple people.
It tries to drive the vampire to kill Buffy by reminding him of his "true" nature (Angelus) and it sets about accomplishing this by appearing to him as some of his victims: Daniel, Margaret, Travis and Jenny Calendar.
Later, the First makes its presence known again in the seventh season by tormenting the vampire Spike, who like Angel has come into possession of a soul; tricking the former villain Andrew Wells into awakening the Hellmouth beneath Sunnydale High; and dispatching its agents, the Bringers, to kill young women around the world with the potential to succeed Faith as the current Slayer.
Though incorporeal, the First is effective in prompting suicides, deceiving various members of the Buffy's gang, and releasing evil monsters from the Hellmouth.
Later in season 7, the audience is introduced to the First's right-hand-man, the supernaturally strong misogynistic ex-priest Caleb, as well as its army of primordial Turok-Han vampires living beneath the Hellmouth.
For instance, the First appears as Warren to get Andrew to kill Jonathan during "Lessons," as Eve to more easily attack the Potentials during "Showtime," and as Buffy to amplify Spike's torture throughout season 7.
In Chaos Bleeds, the First displayed the ability to possess people, open portals, teleport beings across dimensions and, according to Sid, conjure a duplicate dummy body for him and trap his soul inside.
The First Evil has appeared in 16 canonical Buffyverse episodes: Buffy the Vampire Slayer The First appears in the non-canonical video game Buffy the Vampire Slayer: Chaos Bleeds as the main antagonist, having helped occultist magician Ethan Rayne escape military confinement to enact a plan for world domination.
Buffy and her friends pursue the First over multiple realities and across the centuries, eventually "dispersing it across dimensions" to stop its plans to consume the universe with evil.
They are humans who have been corrupted by the First and undergone rituals that include self-mutilation: their eyes and tongues are removed, and their eyelids covered by rune-like scars; yet they are perfectly aware of their surroundings.
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.
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.