Salazar Slytherin is assumed to be born during the first millennium (A.D). He was raised in a pureblood family and along with his family, he had the gift of Parseltongue. When picking students to be in his house, Salazar prized in picking students with the qualities of resourcefulness, determination, and a certain disregard for the rules, along with the ability to speak Parseltongue. He also picked students based on their ambition, cunning, and their blood purity. The reason Salazar was so picky about blood purity was because he mistrusted Muggle-borns. When he suggested the idea about not letting muggle-borns into the school to the other founders, they all disagreed with him, causing him to leave the school. This thought caused so much tension between Gryffindor and Slytherin that it is said that they dueled and a civil war broke out between the houses. When he left the school, Salazar Slytherin left behind the Chamber of Secrets and the Basilisk. <a href="https://ibb.co/3mtL8PP"></a> Source: https://harrypotter.fandom.com/wiki/Salazar_Slytherin Belle Lestrange, Assistant Manager and Publisher