Hagrid, Hogwarts' Gamekeeper
Hagrid is the giant gamekeeper at Hogwarts. He has become very good friends with Harry, Ron, and Hermione- especially with Harry. Hagrid is the one who came to the muggle world to rescue Harry from the Dursleys, who wouldn't let him read the huge abundance of letters he was recieving inviting him to go to Hogwarts.
Ever since, Hagrid has been helpful to the friends, and sometimes the opposite, although Hagrid would never deliberately do anything to get them in trouble. He has a soft spot for having monsters as pets, including dragons and huge spiders.
50 years ago, when the chamber monster was killing people, Hogwarts banished Hagrid from school because they thought it was his pet huge spider that was doing it (it wasn't.) When it happended again, he was sent to the Prison of Azkaban, but released eventually. He now lives in a little hut on the grounds peaceful and content(usually.)