Through an act of will, Madison Jeffries can "phase into" the humanoid robotic body called Box in order to control it from within. The Box robotic body is principally composed of a "living metal," whose exact nature has not been revealed. Jeffries mentally controls Box from within its body, and he can perceive whatever its sensors perceive. Although Jeffries cannot actually feel physical pain while within Box, his psychic link with Box is so strong that he can feel psychic pain of enough force is inflicted upon Box.
The Box robot has vast superhuman strength and is highly resistant to physical damage. Powerful jets in the soles of its feet enable the robot to fly.
Box also contains many different devices to fill various functions. In fact, Jeffries can use his psionic powers to create new equipment for Box, or to modify existing devices within Box, or to alter Box's shape, in any way that he can conceive that is physically possible. For example, he has caused part of Box's body to become a cannon. When Box flies, he causes its arms to become wings and a rudder to appear on its feet. He has caused a drill to emerge from Box's feet.
Jeffries is able to alter the robot as needed such as forming weapons or adapting sensors. By drawing upon outside material, he can increase the size of the robot to unknown limits. When last seen, he had developed prototypes for the Weapon X Project and seemed able to control them simultaneously.