Hogwarts is divided into four houses, each bearing the last name of its founder: Godric Gryffindor, Salazar Slytherin, Rowena Ravenclaw and Helga Hufflepuff. The houses compete throughout the school year, by earning and losing points for various events, for the House Cup. Each house also has its own Quidditch team that competes for the Quidditch Cup. These two competitions breed rivalries between the houses. Houses at Hogwarts are living and learning communities for their students. Each house is under the authority of one of the Hogwarts staff members. The Heads of the Houses, as they are called, are in charge of giving their students important information, dealing with matters of severe punishment, and responding to emergencies in their houses, among other things. Each year, year level groups of every separate house share the same dormitory and classes. The dormitory and common room of a House are, barring rare exceptions, inaccessible to students belonging to other Houses.
Slytherin house values ambition, cunning, leadership, and resourcefulness; the Sorting Hat said in Harry Potter and the Philosopher's Stone that Slytherins will do anything to get their way. The house mascot of Slytherin is the serpent, and the house colours are green and silver. The Slytherin motto is "Slytherin will help you on your way to greatness". Salazar Slytherin founded the house. The Head of House is Severus Snape until near the end of the sixth book. Then, Horace Slughorn, the previous Head of House, comes out of retirement re-assuming authority. Slytherin corresponds roughly to the element of water. The Slytherin dormitories and common room are reached through a bare stone wall in the dungeons. The Slytherin common room is a long, low, dungeon-style room, located under the Hogwarts Lake, furnished with green lamps and carved armchairs. The room is described in the second book as having a greenish glow.
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