Major Grady Ellison commands the specialized "Gigantic Thunder" squadron within the North American Allied Forces. A veteran pilot with extensive combat experience across multiple theaters, he has operated AMAIM units since their initial deployment.

His expertise lies in piloting customized, high-performance AMAIM variants. He began with a blue customized Brady Hound, the "Brad Exclusive." Later, he transitioned to a black high-performance Brady Phantom unit. This specific AMAIM integrated the AI derived from Prototype Zero Ghost and removed pilot safety features like shock absorbers to maximize combat effectiveness. He was subsequently assigned the NA15S Aaron Rhino, the Brady series successor deployed during the events of "Ultra-Steel Ogre Gear." His "Grady Special Machine" Aaron Rhino, distinctively colored blue, replaced the standard knife with a sword stored on the left hip and featured a dedicated high-output shoulder thruster unit, emphasizing close combat alongside its short-barrel rifle.

During the "Ultra-Steel Ogre-Gear" conflict, Major Ellison led the Gigantic Thunder battalion against the Japanese resistance group "Hinukan" on an island. His forces engaged both Hinukan fighters and mercenary Jin Misawa piloting the Protogouyo MAILeS. The conflict culminated in a direct confrontation between Ellison in his Aaron Rhino and the wounded Jin Misawa, resulting in Jin Misawa's death due to his injuries. Ellison survived this engagement. The overall battle against Hinukan and NAC forces concluded with resistance member Ibuki Chinen surviving to continue guerrilla operations.