The children later find out that Fluffy is guarding the philosopher's stone, an object that has the power to turn any metal into gold and produce a potion that grants immortality. Harry suspects that the Potions teacher and head of Slytherin House Severus Snape is trying to obtain the stone in order to return Voldemort to physical form. Hagrid accidentally reveals to the trio that Fluffy will fall asleep if music is played to it. Harry, Ron, and Hermione decide that night to try and find the stone before Snape does. They discover an already asleep Fluffy and face a series of safeguards, including a deadly plant known as Devil's Snare, a room filled with aggressive flying keys that bruise Harry, and a giant chess game that knocks out Ron.