Lego Rock Raiders was a Lego theme introduced 1999, and discontinued in 2000. Rock Raiders was the only theme in the Lego Underground series before Lego Power Miners. The theme, while short-lived, featured sixteen sets and was backed-up by numerous story-related media, including several comic books and video games.The premise of the story involves the crew of the LMS Explorer. The vessel is damaged after wandering into an asteroid field and is sucked into a wormhole, the wormhole exits in an alien galaxy, parallel to the Milky Way. The LMS Explorer's captain orders the ship to use its reserve power and head for the nearest planet. The planet is abundant in the mysterious but powerful Energy Crystals. There the Rock Raiders, whilst repairing the ship, must venture inside the dangerous caverns of the planet to collect the precious Energy Crystals to power the ship.