M15: Mother Lode is the fifteenth mission in Metroid Prime: Federation Force. It takes place on Excelcion. The Federation Force is tasked with infiltrating an abandoned Galactic Federation mine that has been overtaken by the Space Pirates. They must escort a Cargo Tram filled with minerals to the planet's surface. During the mission, Space Pirates and Zurburats attack the soldiers, and the tram. Parasites are also present. The tram has a machine gun mounted on it, but it has a slow rate of fire. If necessary, the tram can be stopped. The tram will eventually reach a spaceport and must be defended until it and the Force can be extracted. The bonus objective is to kill 20 Zurburats, which can be easily done when the tram is going down one corridor. Zurburats spawn in large numbers behind it.