Sheyvan was a Force-sensitive assassin who, in the early years of the Galactic Empire, served as one of the Emperor's Hands. He was assigned to train the cloned stormtroopers of the deceased Dark Jedi Sa Cuis in the techniques of lightsaber and Force combat.
Sheyvan eventually discovered that he was not the only Hand in the service of Emperor Palpatine, as he had been led to believe. He was bitter about it, but he remained loyal to the Emperor and Darth Vader, at least until the right opportunity would show itself.
On the planet Yinchorr, Sheyvan showed a demonstration of his stormtroopers to the Emperor, Vader, and Erv Lekauf. After they proved successful against the clones of Lekauf, the Emperor ordered Sheyvan and the clones to return with him, Vader, and Lekauf to Coruscant. He planned to train the Cuis clones further and incorporate them into the 501st Legion.
En route to the capital, about half-way into the journey, Sheyvan and his troopers suddenly hijacked the Lambda-class shuttle and planned to kill the Emperor. Darth Vader, Lekauf, and Lekauf's clones fought their way through to the hatch that Sheyvan and his men sealed off. In a tense battle, Vader killed all of the Sa Cuis clones while Lekauf was left injured with severe burns from a flamethrower. Sheyvan explained to Vader that the Emperor was using everyone and asked him to help overthrow the elder Sith Lord. Vader, though tempted to claim the galaxy for himself, refused and after a quick lightsaber duel, Sheyvan was killed. However, despite holding back fire and surviving smoke, Sheyvan was a still formidable fighter, and Vader admired this. He genuinely regretted the final stroke that sliced Sheyvan shoulder to hip and left him for dead on the deck.