A prequel to "A Town Called Mercy" was released exclusively onto iTunes, and titled "The Making of The Gunslinger". It depicts the actual making and formation of the Gunslinger, from a normal humanoid body. It also has an explanation of the making of the Gunslinger in voice-over by Kahler-Jex.
Kahler-Jex is in a lab, announcing that "subject 6", Kahler-Tek, has been activated. The Kahler-Tek cyborg raises up his arm weapon and a light emanates from it.