Samantha and Bourne are a pair of pilots who were the leaders of the Dark Forces, a bandit group who operated in the deserts outside of Blue City. They piloted a Brachiozilla (Brachio Rex) and Missile Tortoise, which had the rather unexpected ability to fuse into the Brachio Tortoise. The group attacked the Mach Storm team in order to steal a cargo that Haldo was transporting.

(Source: Wikipedia)