Cyvus Vail was one of the most powerful beings in Los Angeles, with metaphorical tendrils extending throughout the city, obtaining and ensuring his power thanks to his vast wealth, his magical power and his membership of the Circle of the Black Thorn.
After Angel agreed to take over the Los Angeles branch of Wolfram & Hart in exchange for a new life and memories for Connor, Vail was the leader of the elite team of powerful sorcerers hired by the firm to reshape reality and alter the memories of those involved in Connor's life. Afterwards, Vail kept an Orlon Window, a magical artifact that allowed him to observe reality as it was before the alteration.
In the following months, Vail managed to obtain the Resikhian Urn in which the demon Sahjhan, had been trapped by Justine Cooper. Sahjhan was an old enemy of Vail, and had tried to kill him many times, for which Vail sought to have the prophecy of the Nyazian Scrolls (The one sired by the vampire with a soul shall grow to manhood and slay Sahjhan) fulfilled.
Connor was able to kill Sahjhan after Wesley smashed the window. Afterwards, Vail disappeared until Angel was inducted into the Circle.
Wesley Windham Price was chosen to kill Vail by Angel when the team decided to kill the Circle of the Black Thorn. However, Vail easily dominates Wesley, claiming he "craps better magic than that", and fatally stabs him with his own knife. In the end, a grief-stricken Illyria shatters his head with a single punch after he taunts her to take her "best shot".