Crost was a male Twi'lek from the planet Ryloth who was a member of the Free Ryloth movement during their attempt to assassinate Emperor Sheev Palpatine and the Sith Lord Darth Vader. He was a member of Isval's crew, who were responsible for infiltrating the damaged Star Destroyer Perilous disguised as a repair crew and destroying it. The group managed to successfully reach the ship's hyperdrive and set charges, escaping in an Imperial escort boat before the ship exploded. Crost was killed when Vader caused the boat to crash into Ryloth's surface.