In a bid to take over the world, Dr. Doppler creates Limited, a Replibrain with the ability to evolve machines while taking control of them. Desiring combat data to further refine his creation, he sends his biomechanical parasites to revive four previously destroyed Mavericks: Flame Mammoth, Bubble Crab, Wire Sponge, and Boomer Kuwanger. In addition, Dr. Doppler also employs the Reploid assassins Curtiss and Schmitt to monitor the revived Reploids as they attack X.