Rupert Giles was the Watcher and father figure of Slayer Buffy Summers, the former librarian of Sunnydale High School, and the occult expert of the Scooby Gang.
Born into a family of Watchers, Giles initially rebelled and dabbled in sorcery with his friends, including Ethan Rayne, until the death of one of the group led him to return to his family. His grandmother Edna got him help for his magic addiction after which he was allowed to return to the Council.
Despite now putting forward a proper demeanor, he still tends to be rebellious, and he often shows incredible loyalty and protectiveness to those he cares about.
As the Watcher of Buffy Summers, Giles developed a father-like bond with his charge, not only training her but also fighting by her side. During the time leading up to the battle with the Mayor, he openly defied the Council in order to save Buffy's life, leading to his dismissal from the Council.