The gel itself is quite inert. It is a ferrous polymer, one that is somehow highly reactive to internal magnetic fields, but not to external ones. It seems it has a tendency to form three layers, an outer skin, which is like hard, malleable plastic, and which forms on the edge of any mass of the gel, an active soup, which stretches and contracts depending on the magnetic field it interacts with, and which causes a magnetic field when it is distorted, so providing feedback, and an inner skeleton, which provides support for the mass, anchoring onto the body, and also serves as the 'nervous system', transmitting messages between the gelmass and the user. The gel can change colour, forming prismatic, chameleonic shades that shimmer across the surface of the gel.
As the user becomes more adept, they can cause the skin to harden, or deepen, or thin, they can cause the soup to stretch and contort with great strength and finesse, they can cause the skeleton to form long, spindly tubes or short, solid bones, they can cause the gel to form specific coloured patterns, acting as camoflauge.
The control drug puts the user in the right frame of mind to accept new sensory input from the gel, and to send new motor output into it. It is also psychoactive, about as potent as LSD.