"Not much to go on. Salazar Slytherin believed magical learning should be kept within all-magic families. In other words, pure-bloods. Unable to convince the other founders he decided to leave the school. He built a hidden chamber in this castle, known as the Chamber of Secrets. Shortly before departing, he sealed it, until that time when his own true heir returned to the school. The Heir alone would be able to open the Chamber, and unleash the horror within, and by so doing, purge the school of all those who, in Slytherin's view, were unworthy to study magic." 