He appeared in two stories (The Time Meddler and The Dalek Masterplan) as an adversary of William Hartnell's Doctor.
The Meddling Monk was the possessor of a Mark IV Tardis and said he left the Doctor's (then unnamed) home planet some fifty years after he did. This information would reasonably indicate that he was probably a Time Lord, although it was never stated at the time since the concept of the Doctor's race had not yet been devised.
The Monk differed from The Master in that he was not a mass murderer or would be world conqueror. Rather, he liked to meddle in history and to change it for his own amusement. In The Time Meddler, he attempted to prevent the 1066 Norman Invasion.
His final fate has never been revealed.