Herpo the Foul is a villain from the Harry Potter series. He was an Ancient Greek Dark Wizard who was said to be one of the most powerful and influential Dark magic users in all of Harry Potter history.
Little is known about Herpo the Foul, but it has been shown that he was a very powerful wizard who used and invented the darkest forms of magic. He was best known as the first wizard to hatch a Basilisk. He was also the first wizard known to successfully create a Horcrux – accordingly, he has committed deliberate murder to do so, and using his already damaged soul to his advantage to obtain immortality. His contributions of Dark Magic has an eternal impact on the magical society, and the act of creating the Horcrux is regarded as the darkest form of magic, and possibly the only one that is considered purely evil magic.
Herpo was also one of the earliest known Parselmouths. He might have been an ancestor of Salazar Slytherin because of his ability to speak to snakes.
It is unknown how/if he died and who destroyed his Horcruxes. Some Harry Potter fans think that his Horcruxes were destroyed by the venom of his own Basilisk, as it is one of the few things that can destroy a horcrux. Other don't even know if he died due to lack of information on him.
He was well known for influencing Lord Voldemort as he used a Basilisk to purify Hogwarts and he also sought Horcruxes to gain immortality.