Blanch Sproull was a human mechanic in the Alliance to Restore the Republic, holding the rank of private. Sproull left the mining planet where they resided to join the Rebellion, believing in its cause. They served aboard the transport Spirit of Jedha when it and several others evacuated the rebel outpost on Lowik. Despite Sproull checking the hyperdrive converter, it malfunctioned mid-jump, and the Spirit of Jedha came under attack from the Ohnaka Gang pirates. The bounty hunter Beilert Valance, who was sent by Lieutenant Kondra to rescue the rebels, failed to defend the transport, and Commander Hill Purpura had him imprisoned aboard the vessel, doubting his allegiance. Purpura left Sproull to guard Valance while he negotiated a surrender with the pirates, but Sproull freed Valance, allowing him to take a semi-functional X-wing starfighter.