There are no shortages of evil figures in the Harry Potter universe, with the likes of Voldemort and Grindelwald mingling among many other dark witches and wizards. Things like Horcruxes aren't only related to Voldemort, as their roots go far back before Voldemort was even born. The Wizarding World actually has an extremely dark and violent history that precedes the main chronology, and it's interesting to follow the timeline of these events.
These events begin before Hogwarts was constructed and lead all the way up to Voldemort's defeat to give a clear picture of the darkest periods in wizarding history.
Before 100 AD, Herpo the Foul becomes the first dark wizard in history by committing a number of heinous acts. He first experiments with magical creatures to figure out how to create a basilisk. He achieves this by hatching a chicken's egg under a toad, which breeds a serpent that grows to enormous lengths. It is believed that this serpent is the same basilisk that Salazar Slytherin later housed in the Chamber of Secrets.
Around that time, Herpo the Foul dives deeper into dark magic by splitting his soul in two. He does so by slaying an innocent person and inventing a curse that tears apart his corrupted soul. Herpo then seals the soul into a receptacle to make it the first Horcrux.
Sometime later, Herpo the Foul feels genuine remorse for what he did, and this leads to his soul becoming one again, but it is believed that this caused his demise.
9th Century: The Dark Wizard Godelot Advances The Study Of Dark Magic - And Is Slain By His Son
During the 9th Century, the dark wizard Godelot compiles a vast knowledge of evil spells into one book that he titles Magick Moste Evile. Godelot has slain the former owner of the famed Elder Wand and become its master. He uses the Elder Wand to commit further evil acts that help him in writing his book.
However, Godelot's pursuit of power is dashed when his own son, Hereward, is consumed by similar greed and locks his father in a cellar. After Godelot's demise, Hereward becomes the master of the stolen Elder Wand.
11th Century: The Bloody Baron Murders Helena Ravenclaw
During the 11th Century, the great witch and co-founder of Hogwarts, Rowena Ravenclaw, is on her deathbed and wishes to see her daughter. Helena Ravenclaw is a treacherous witch who has betrayed her mother's love by stealing her diadem, but has failed to gain any wisdom from it as she hoped. Rowena sends a dark wizard to bring her daughter back to her, who then tracks Helena down in Albania.
When she refuses to return with the man, who has been in love with her this whole time, he's seized by immense anger and proceeds to kill her. After realizing the horror of his actions, the wizard takes his own life out of guilt and the diadem is left hidden inside of a tree.
Soon after, Helena Ravenclaw returns as a ghost named the Grey Lady and ironically goes back to Hogwarts where her mother had always wanted her. The wizard becomes a ghost known as the Bloody Baron, again following Helena in death to Hogwarts.
By the 14th Century, attacks on Muggles through dark magic have become so common that non-magic folk have taken to apprehending suspected witches and burning them. The Wizarding World is quick to catch on to this, however, and magical people start carrying their wands around at all times to escape a burning.
Some witches begin to enjoy fooling Muggles so much that they deliberately get themselves put at stake just to escape. The witch known as Wendelin the Weird uses 47 various disguises to be burned and escapes each time by using a Flame-Freezing charm.
During the 15th Century, the evil wizard known as Ekrizdis finds an abandoned rock in the middle of the North Sea and uses it for his malicious plans. He creates a fortress that is unplottable by Muggles and cannot be found by wizards either unless he wants them to. Ekrizdis lures unsuspecting Muggle sailors to his lair, where he proceeds to mercilessly torture and kill them.
Many years later, Ekrizdis passes, which lifts the concealing enchantments around his lair, and the Ministry of Magic eventually finds it. Upon entering, they find the place to be infested by Dementors, frightening them so much that the Ministry decides to leave the fortress as it is.
1717: Three Dark Curses Are Deemed Unforgivable By The Ministry Of Magic
In 1717, the Ministry of Magic can no longer ignore the many evil acts that wizards have openly committed due to the lack of regulation. To this end, a new law is passed that absolutely prohibits the use of three curses that are deemed the "Unforgivable Curses." These are the Cruciatus, Imperius, and Avada Kedavra curses, which allow wizards to torture, mind control, and kill anyone through the successful execution of the spells.
In order to ensure that these curses aren't used, the Ministry treats any occurrence of the spells' implementation as an offense that will land a wizard in jail.
