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I think it... You do it.
~ Ken Castle to John "Kable" Tillman

Ken Castle is the main antagonist in the 2009 film Gamer.

He is portrayed by Michael C. Hall of Dexter fame.


Castle is an exceedingly wealthy and expertly skilled computer programmer who has discovered the use of self-replicating nanites in the year 2024. These nanites mimic brain cells and can be used by a person to control another person's bahaviour and actions, much like a video game character - Castle has named this new technology Nanex. Castle had gained his monstrous fortune by creating two real-life video games: the first, called Society, is a game where the player controls a real person in a pseudo society and makes them perform various actions (anything from verbal interactions to making love with a total stranger). The people being controlled have consented to this and are paid very well for participating. The second game, called Slayers, is a real-life first-person shooter game where players control death row or life imprisoned inmates, and if the inmates survive thirty rounds, they are granted their freedom.

Although incredibly popular, Castle's technology also sparks a large amount of debate in terms of ethics, and an activist organization named Humanz claims that Castle will eventually use the Nanex technology to gain control of people's minds against their will. When Castle had been testing the effectiveness of Nanex, he personally controlled a man named John Tillman and forced him to fatally shoot his own friend. Tillman had been placed on death row as a result but volunteered to participate in Slayers in the hopes that he may earn his freedom (where he gained the nickname Kable). After surviving a record twenty-seven rounds, Castle begins to feel threatened by Kable's pending release and subsequently sends another inmate, named Hackman, into the game to eliminate him. Unlike the other inmates, Hackman is not controlled by a player and is able to act freely, giving him a huge advantage over Kable.

With the help of the player controlling him, Kable is able to escape from the Slayers battleground and is contacted by Humanz, who inform him of Castle's subtle plans for world domination. Kable eventually confronts Castle and the evil mastermind reveals to him that he himself possesses nanites in his own brain as well - however, whereas everybody else's nanites are programmed to receive orders and instructions, Castle's are designed solely to give them. After killing Hackman in a brief fight (during which time Castle had been controlling Hackman), Kable attempts to kill Castle with a knife but is unable to due to Castle's control over his own nanites. Castle then attempts to force Kable to kill his own daughter, but unbeknownst to him, the Humanz organization broadcast this and show the world Castle's true nature. Kable's player witnesses the broadcast and immediately takes back control of Kable, allowing him to overcome Castle's commands, much to his horror. Kable and Castle struggle for control of the knife, until Kable tells Castle to imagine the knife penetrating his stomach - Castle subconsciously does so, making it come true and allowing Kable to fatally stab him.