Slytherin 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. Throughout the series, until the seventh book, the Head of House is Professor Severus Snape. Then, the previous Head of House Professor Horace Slughorn comes out of retirement, re-assuming authority after Snape becomes headmaster. The ghost of Slytherin house is The Bloody Baron. According to Rowling, Slytherin corresponds roughly to the element of water. The founder of this house is Salazar Slytherin.