Are the Master Chief and Doom Guy the same person?
I have always insisted that John 117 and Doom are the same person. I mean, particularly because they share the same obvious name, "John". So, what really happened in my brain to claim such controversy? Well, the stories just click, I mean, think about it. If you have played Halo 4, you should already know that the Master Chief is a Forerunner, and he goes way back, and by that, I really mean thousands of years back.

When the Master Chief and The Didact faced off for the first time, The Didact used power that John had never been a victim of. So what happened to the Master Chief then? The Didact was trying to use the composer on him, yet he was unable to. The Didact then discarded him away but at the same time split part of him. His soul, unseen, was then sent to another dimension when…
