Angel (season 1)
At the end of the third season of "Buffy", the 242-year-old, re-ensouled vampire Angel left Sunnydale to give teenage Slayer Buffy Summers the chance to live a normal life. Angel is now living in the big city of Los Angeles. With Buffy gone Angel is now completely cut off from society, every day getting closer and closer to giving in to his vampiric hunger. It's not until he befriends the half demon and fellow Irishman Doyle, who is sent visions of people in trouble by The Powers That Be, and fellow Sunnydale resident Cordelia Chase, who grounds Angel's life in the humanity around him, that he truly begins to take charge of his life and seek atonement for his past sins. He sets up his own detective agency, Angel Investigations and begins to "help the helpless".
List of Buffy the Vampire Slayer characters
Cordelia is originally an archetypal popular, shallow, mean-spirited cheerleader. She is tactless, but direct and honest, and she becomes a reluctant ally of the Scooby Gang, even after her relationship with Xander disintegrates. After season 3, she joins Angel in L.A., where she abandons her attempts at acting to fight evil at his side.
Angel, a vampire, formerly known as Angelus, was a cruel killer until he was re-ensouled by a Romani curse. After decades of guilt over his past atrocities, he allies himself with Buffy and they fall in love. The consummation of their relationship brings him a moment of true happiness, breaking the curse and releasing Angelus upon Sunnydale. Buffy is forced to send him to a hell dimension to save the world. After his release from hell, Buffy and Angel continue to struggle with their ongoing love. Angel breaks off their relationship and moves to L.A. (after season 3) to give her a chance at a more normal life. There, he gathers new allies in his own fight against evil in the five-season spin-off, "Angel".
Oz is a brilliant (yet generally unmotivated) student, and part-time rock guitarist. He is Willow's first and only boyfriend, and an active member of Buffy's inner circle, despite the fact that he has recently become a werewolf. Portrayed as taciturn and unflappable, the contrast between his outward coolness and his violent animal episodes is an example of the show's efforts to subvert usual character expectations, as well as to display double-personalities (like Angel/Angelus). As an unusual side-note, the actor Seth Green went on to co-design and supervise the creation of the acclaimed line of "Buffy the Vampire Slayer" action figures.
Spike is a vampire character whose role varies dramatically through the course of the series, ranging from a major villain to "love's bitch", to the sarcastic comic relief, to Buffy's romantic interest in a relationship that grows from miserable lust to a friendship, and eventually to a self-sacrificing hero, dying as a Champion at the Hellmouth. His path to redemption subsequently resumes in L.A. (in season five of "Angel"), where his resurrected character continues to develop into a selfless hero and reconciles with his former nemesis and love rival, Angel, and occasionally works with him. Spike is known for his Billy Idol platinum hair(Angel mentions in one episode that Spike doesn't style his hair like Idol's, but the other way around), his catch-phrase "bloody hell", and his black leather duster, which he acquired after killing his second Slayer.
Anya is a 1,120-year-old former vengeance demon (Anyanka) who specialized in avenging scorned women. After being forcibly stripped of her demonic powers by Giles, the character is forced to re-learn how to be an ordinary human, a journey which is portrayed as both comical (e.g., her fear of rabbits and her love of money) and poignant (e.g. her grief over Joyce's death). Her story is largely focused on her romantic relationship with Xander, and like many characters on the show, she is portrayed as morally ambivalent.
Riley is Buffy's first serious boyfriend after Angel. He is initially an operative in a military organization called "The Initiative" that uses science and military technology to hunt down HSTs or "hostile sub-terrestrials" (demons). Riley is Angel's opposite, an Iowa-born-and-raised man whose strength lies in his military secret identity. Buffy's superior physical strength causes him insecurity, particularly after his medically enhanced powers were removed. This, combined with Buffy's inability to truly emotionally connect with him, eventually causes him to leave in the middle of Season 5.
Dawn is introduced in Season 5 as Buffy's fourteen-year-old younger sister, sent to Buffy in human form as a disguise for the Key, a dangerous magical artifact sought by a hellgod. Although Dawn's genesis is magical, she functions as a complete and normal teenage girl, and, after her true nature has been revealed, she is accepted and loved as a sister, daughter, and friend. Although Buffy initially tries to shelter Dawn from her work as Slayer, Dawn later becomes a useful member of the Scooby Gang.
Tara is introduced first as a fellow member of a Wicca group during Willow's first year of college. Their close friendship evolves into an ongoing romantic relationship; their relationship attracted significant attention as one of few featured same-sex relationships on television at that time. Tara uses her magical skills to assist the Scooby Gang in their fight against evil, and she struggles with how to deal with Willow's growing addiction to magic. Tara is killed by a bullet intended for Buffy, her death triggering Willow's transformation into "Dark Willow".