Unidentified rogue Jedi

Thousands of years before the Clone Wars, a rogue Jedi studied the forbidden arts of the dark side of the Force and was exiled from the Jedi Order. He and his followers sparked the period of time known as the Hundred-Year Darkness, from which the Sith were born.

Biography
Thousands of years before the Clone Wars, this male was a member of the Jedi Order. At some point, he began studying the forbidden teachings of the dark side of the Force and believed that the true potential of a Jedi involved tapping into the dark side, as opposed to embracing contemplation and passivity of the light side. The Jedi High Council, upset by the beliefs of this rogue Jedi, exiled him from the Jedi Order. The Dark Jedi gained a number of followers, and their actions led to formation of the Sith, an order born during the Hundred-Year Darkness. At the end of this period, the Sith had been born to practice the dark side and became the mortal enemies of the Jedi Order.