The character played by Michael Gambon in the "Harry Potter" series was the founder of what organization?
Michael Gambon:  Gambon has played the eponymous mystery writer protagonist in the BBC television serial "The Singing Detective", Jules Maigret in the 1990s ITV serial "Maigret", and Professor Albus Dumbledore in the final six "Harry Potter" films after the death of previous actor Richard Harris. Albus Dumbledore:  As part of his backstory, it is revealed that he is the founder and leader of the Order of the Phoenix, an organisation dedicated to fighting Lord Voldemort.
Order of the Phoenix