The Fire Legion is a terroist organization created in response to the energy crisis on Terra II. They are made up by members of nation's who lost the Unification Wars, such as Gyaros. Their ultimate goal is to sieze control of the planetary government and take all the energy resources for themselves. They gain recruits under the guise that they want to give energy to the people, which is not the case. They were responsible for the attempt on Kochi Shima's life, because they saw him as a potential obstacle in their path.
After Tetsu and Laika's escape from Shima Industries, they join the Fire Legion. Tetsu seizes control of the group for himself by killing the current leader and turning the legion into his personal vehicle for revenge. They discover some Yoma mechs and use them, oblivious of their origin. They are the ones who eventually awaken the Yoma. The Fire Legion then enters into a uneasy alliance with the TDF to destroy the Yoma threat.