Mysterious events start to happen when the government Earth Corps unearths an amber monolith in a forest; meanwhile, an unscrupulous businessman, Blackthorn, digs up a vine creature, Tendril, which frees the trapped undead beast, Decompose. Earth Corps must use their specially-designed armoured suits to track down the enormous monsters. In the process, the dormant Mutar species of Redwoods, Granites and Magnacore are reawakened, and join forces with Earth Corps to once again do battle with their centuries-old enemies, the Inhumanoids, in an effort to save the world.