|“||We'll teach just those whose ancestry's purest.||„|
|~ Slytherin's opinion regarding the running of Hogwarts.|
Salazar Slytherin is an outspoken character in the Harry Potter series. He is one of the four founders of Hogwarts who founded the House of Slytherin and the ancestor of Lord Voldemort, and is thus the posthumous overarching antagonist of the franchise.
Salazar Slytherin was one of the first recorded parselmouths (wizards that have the extremely rare ability to speak to snakes). When he founded Hogwarts with the other three founders, he chose students that show traits of resourcefulness, leadership, ambition, cunning, shrewdness and determination.
Salazar Slytherin wanted to be more selective of the students admitted to Hogwarts. He believed that the school should only accept pure blood witches and wizards, as he distrusted Muggle-borns, possibly of the great conflict between Wizardkind and Muggles. He tried to sway the other founders to agree with him but they refused, especially Godric Gryffindor. This caused Salazar Slytherin's friendship with Godric Gryffindor to break and resulted in him leaving the school.
Salazar Slytherin is known to have been the creator of the Chamber of Secrets. He created it in a hidden part of the school. He managed to breed and keep a Basilisk in the chamber. He would later use the basilisk to purge Hogwarts of any and all Muggle-borns. The other founders did not know of this and were likely unaware that it was Slytherin's doing.
It is unknown when or how he died, but it is known that his portrait is still at Hogwarts and his locket was made into a horcrux by Voldemort.
Many Harry Potter fans consider Salazar Slytherin to be a Dark Wizard because he wanted to purge Hogwarts of all the Muggle borns and because he is a parselmouth. Another reason could be that many Dark Wizards and Witches came from the house of Slytherin. Even though the author J.K. Rowling has not stated whether Salazar Slytherin is evil or not many of her fans believe that he is.
Slytherin's bloodline was passed down through the female line for generations. The Gaunt family, who practised inbreeding by marrying their own cousins, in order to keep their bloodline pure and their ability to speak Parseltounge, were the last known family to possess Salazar Slytherins blood. Among the last of the Gaunt's included Marvolo Gaunt and his two children Morfin and Merope. Merope fell in love with a Muggle named Tom Riddle and eloped with him, while her father and brother were in Azkaban. Eventually Tom and Merope's marriage resulted in the birth of Tom Marvolo Riddle, later known as Lord Voldemort.
After Voldemort's death, everyone thought that Slytherin's bloodline had ended. It was later revealed in the "Harry Potter and the Cursed Child" stage play that Voldemort had a daughter with Bellatrix Lestrange, her name was Delphini. As of 2020, Delphini is the last survivor of the Slytherin bloodline.