Who is Ebenezar McCoy from Blood Rites and what is their importance?

Ebenezar McCoy is the wizard that took Harry in to live with him after Harry's uncle died. Harry had thought the man had very strict rules on right and wrong but is told by Kincaid that Ebenezar was called Blackstaff McCoy and given sanction by the White Council to break the law where he saw fit in order to stop those that were outside the law. Harry also learns that it was Ebenezar that trained his mother. Harry feels betrayed and lied to and eventually tells Ebenezar to get out and never come back.