Former Jedi Master A'Sharad Hett of the Old Republic, after being captured by the Yuuzhan Vong, managed to break free from his confinement. He then sought refuge on Korriban, where he swiftly adopted the identity of Darth Krayt and established the One Sith.
Following the fall of the Jedi Order at the conclusion of the Clone Wars, A'Sharad Hett, who was a Jedi Master, made his way back to his native planet, Tatooine. There, he assumed command of a Tusken Raider army, only to be defeated by Obi-Wan Kenobi, a fellow Jedi in exile. Forced from his home, Hett ultimately found himself on the Sith world of Korriban, where he discovered the holocron of XoXaan, one of the original Dark Lords of the Sith, and decided to learn the ways of the Sith from it. When Hett finally reemerged, he found that the Galactic Empire had been defeated through the efforts of Luke Skywalker and the Alliance to Restore the Republic. This left him unable to exact his revenge upon the Sith Lords responsible for the Jedi's destruction: Darth Vader and Darth Sidious. Feeling cheated, Hett escaped to the Unknown Regions, only to be taken prisoner by the Yuuzhan Vong, an extra-galactic race. After being captured, Hett endured brutal torture, experimentation, and imprisonment within a torture device known as the Embrace of Pain. While there, he encountered Vergere, a Jedi from before the Clone Wars who had secretly trained as a Sith under Darth Sidious. The two engaged in discussions about the future of the Sith Order, with Hett advocating for an army of Sith to bring order to the galaxy, while Vergere favored Darth Bane's Rule of Two. Unable to reach an agreement and deeming him a lost cause, Vergere abandoned Hett to the Yuuzhan Vong as she departed to assist in preparations for their attack on the galaxy.
Left alone, Hett bided his time until he had amassed sufficient strength in the dark side of the Force to break free from his captivity. During his escape, the former Jedi used Force lightning to attack his captors and commandeered a Yorik-et starfighter to flee the ship. To ensure his survival remained a secret, Hett destroyed the scout ship, eliminating everyone on board before returning to Korriban. There, he adopted the name Darth Krayt, drawing inspiration from the reptilian predators of his home planet. Upon completing his training, he established a new generation of Sith known as the One Sith, while the New Republic was preoccupied with the Yuuzhan Vong and their invasion. Over time, he and his followers steadily grew in strength before emerging and seizing control of the galaxy, with Krayt ascending to the position of Emperor of a revived Galactic Empire. More than a century later, he recounted his escape to Cade Skywalker while torturing him within an Embrace of Pain.