Giant Chess Set

One of the protections for the Philosopher’s Stone.

• After Harry, Hermione and Ron passed through the Devil's Snare and the room with Flying Keys, they came to a room containing a huge chessboard. The chessmen were tall and carved from stone. Professor McGonagall had transfigured them to come to life (PS16).  In order to pass through the room, a person had to take the place of a chess piece and successfully play to win. The game was Wizard's Chess, so there was real danger to any human chess pieces.
• Ron had skill with the game so he took control and decided to become the black knight, telling Harry to take the place of the bishop and Hermione to take the place of the castle or rook (PS16). Then he directed the other pieces silently with magic wherever he wanted to move them. At the end of the game, Ron had to sacrifice himself by letting the white queen hit him on the head so that Harry (the bishop) could move and put the King in checkmate.
• The next room contained a Troll which had already been knocked out by Quirrell, and then on to Snape's Potion Riddle (PS16).