Doctor Gilmer operates as a scientist in the Die-Die Gang, led by Emperor Dongolos and commanded by Mister K across Asia. Under Mister K's direction, he designs and constructs advanced war machines called Devil Mechas, deploying them against Rainbowman and humanity. Gilmer also develops other technological weapons for the organization, including the mind-controlling Seinin Mecha device.

His scientific work takes place within the Die-Die Gang's laboratories and facilities, frequently located in remote mountain bases. He collaborates with Mister K's deputy commanders, such as Fairie Rosé, in developing their technologies. Doctor Gilmer's creations pose critical threats faced by Rainbowman throughout the conflict.