From Half-Life 2
The G-Man is a mysterious and enigmatic character encountered several times in the Half-Life series. Referred to as a "sinister interdimensional bureaucrat",[3] he is known to display peculiar behavior and to wield powers far beyond those of a human. His identity and motives remain completely unexplained. His allegiance also remains unknown to this day. He plays the role of an overseer and eventual employer, watching over Gordon Freeman and other characters as the series progresses, at times helping or hindering them.