Krayn was a T'surr space pirate and slave trader around the time of the Invasion of Naboo.
The Jedi Knight Siri Tachi once infiltrated Krayn's organization. It was discovered that Hala, the mother of Anakin Skywalker's friend, Amee, was taken from her on one of his slave raids back on Tatooine. During a diplomatic mission, Obi-Wan Kenobi's and Skywalker's transport was intercepted by Krayn, and the two Jedi boarded the ship in a small utility vessel and crippled its weapon systems.
As they were approached by Krayn's slaves and guards, Skywalker entered an argument with Kenobi whether to leave the slaves or help them. When they were discovered Skywalker ended up as Tachi's prisoner but Kenobi managed to escape. Together Skywalker and Tachi managed to start a rebellion among Krayn's slaves, and they later met up with Kenobi, who had infiltrated Krayn's facility, hoping to save his young apprentice. In the end, Skywalker defeated Krayn in combat. Ignoring Kenobi's command to spare Krayn's life, Skywalker stabbed the T'surr through the chest with his lightsaber.