What character did this actor, who also played a supporting role in Sleepy Hollow, play in the final six Harry Potter films?
Sleepy Hollow (film):  It is a film adaptation loosely inspired by the 1820 short story "The Legend of Sleepy Hollow" by Washington Irving and stars Johnny Depp and Christina Ricci, with Miranda Richardson, Michael Gambon, Casper Van Dien, and Jeffrey Jones in supporting roles. 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.
Professor Albus Dumbledore