"Or perhaps in Slytherin, you'll make your real friends, those cunning folk use any means, to achieve their ends." The Sorting Hat
Slytherin is one of the four Houses at Hogwarts School of Witchcraft and Wizardry, founded by Salazar Slytherin.
Salazar instructed the sorting hat to choose a few particular characteristics he most valued: cunning, resourcefulness, and ambition.
Its emblematic animal is a snake and its colours are green and silver. The Head of Slytherin is Horace Slughorn and the House's patron ghost is the Bloody Baron.
Slytherin corresponds roughly with the element of water with serpents being commonly associated with the sea and lochs in western European mythology, as well as serpents being physically fluid and flexible animals.
The colours also correspond with waters around lakes and lochs often being green, and silver being often associated with grey rain water.
Phineas Nigellus Black
Tom Riddle (Lord Voldemort)
Regulus Arcturus Black