Salazar Slytherin was a Pure Blooded wizard of medieval times. He was a Parselmouth and very highly skilled at legilimency. He was one of the founders of Hogwarts School Of Witchcraft and Wizadry and the former best friend of Godric Gryffindor. Slytherin did not trust Muggle Born students and expressed his opinion not to accept them at Hogwarts. However when the other founders did not agree, He built the Chamber Of Secrets, concealing the Basilisk inside. Afterwards he fled the school and died somewhere in the Middle Ages.