Ontinald (1215-1245) was the wizard who invented dark magic. He did it in 1237. He created the philosophy that pure-bloods were superior. He fought to make his philosophy followed. He did attract about 18 followers. But those followers were deadly. He murdered countless muggles and muggle-borns. So did his followers. In 1245, he was captured and imprisoned by William Dumbledore, an ancestor of Albus Dumbledore. In 1363, Hogwarts School of Witchcraft and Wizardry was founded. One of the founders, Salazar Slytherin, tried to adapt Ontinald's philosophy. The philosophy remained its existance forever. Yet after Harry Potter destroyed Voldemort for good, the number of followers went drastically downward.