John Lumic is the president and founder of the advanced technology firm, Cybus Industries. He is a genius inventor, having created many technological marvels now commonplace in modern society, such as the EarPod - a small but powerful communications device that allows citizens to download news and other information directly into their brains (these devices were later discovered to be used for mind control as well).
In the Doctor Who episodes Rise of the Cybermen and Age of Steel, the terminally-ill Lumic had devised a means of preserving the human brain so that he might save his own life: a cradle of chemicals harnessing the brain bonded to a robotic exoskeleton. And thus, the Cybermen were born. Intent on "upgrading" the human race, Lumic began abducting homeless people off the streets of London, who would be taken to Cybus's factory in Battersea for cyber-conversion. When Lumic pitched his idea to the President of Great Britain, the President was apalled and forbade Lumic from carrying out his project. Lumic brought his plan forward regardless and sent out the hundreds of Cybermen already built to round up the citizens of London. To establish his domination of the city, Lumic transmitted a control signal to every EarPod across London, turning most of the population into mindless automatons who marched into the Cybus factory without hesitation.
John Lumic was forced to undergo cyber-conversion himself after his traitorous associate Mr. Crane tried to assassinate him by destroying his wheelchair's life-support machine. Crane was killed by Lumic's Cyberman guards but Lumic could not survive without his life-support, and so the Cybermen took him for upgrading. Lumic was transformed into a superior Cyberman - a Cyber-Controller - which could direct the Cybermen through thought alone.
Lumic's plan was thrown into disarray by the Doctor and his companions, with help from anti-Cybus group, the Preachers. They had infiltrated the Battersea factory to shut it down, but the Doctor, Rose Tyler and Peter Tyler were captured and brought before the now-upgraded Lumic. The Doctor's other allies - Mickey Smith and Jake Simmonds - had boarded Lumic's docked Zeppelin airship and hijacked its transmitter, releasing all of Lumic's brainwashed victims. The Doctor secretly relayed instructions to them via Cyber Control's security feed and they were able to uncover the cancellation sequence for the Cybermen's emotional inhibitor chips. With the inhibitors deactivated, the Cybermen within the factory went insane and began to self-destruct, tearing apart the factory as they did. The Doctor and his companions fled, but Lumic - who had no inhibitor chip - tore himself free from his control chair and pursued them. As they climbed the rope ladder into the fleeing Zeppelin, Lumic climbed after them. Using the Doctor's sonic screwdriver, Peter Tyler loosened the rope below him until it snapped. The enraged Lumic screamed as he plummeted down into the exploding factory, where he met his end.