Minerva McGonagall is the Transfiguration professor and head of Gryffindor House. She is also an animagus, possessing the ability to turn herself into a tabby cat. Professor McGonagall is present when Professor Dumbledore leaves Harry on the Dursley's doorstep and strongly opposes his decision to leave Harry with such an unpleasant Muggle family. Although Professor McGonagall is known for being strict, even with the members of her own house, she has a particular fondness for Harry, especially when she sees his spectacular dive for Neville's Remembrall and recruits him for the Gryffindor Quidditch team.
In the attempt to protect the Sorcerer's Stone from Voldemort, Professor McGonagall creates the challenge with the giant chess set.