MI said it is related to a well-known storyline that remains unfinished and unresolved. It sounded like he sees this game as a way to conclude that storyline which never got complete resolution. He also never said that this storyline was originally from an existing game series. I'm trying to think of words ending with X.
Maybe it's related to the Neverending Story? The main character's name in the book is Bastian
Bux. Also, the horse's name is
Artax (pronounced like "Artex" in the movie). Maybe it's inspired by this 2002 game? The Neverending Story: Auryn Quest:
http://www.aurynquest.com, trailer here:
http://www.youtube.com/watch?v=oLyzfpZUB5E - I'm kind of stretching here.
Or maybe it's related to the
Matrix movies.
I like the
DOSBox suggestion that someone else gave. It was something that had come to my mind earlier when I thought maybe he was making a kind of self-aware, semi-autobiographical game, or a game that is about making games or the people who play them.
Then again, maybe it really is related to an existing game series. There's always Sam and
Max. Or maybe the word
Tex (of Tex Murphy fame) is in the title.
The pandora's
box suggestion is also a good one. Did MI ever have any involvement in this KQ4 VGA project?
http://www.youtube.com/watch?v=qxFMr4Izw-0
Maybe plans for a proper KQ4 remake were scrapped, but art and other work was put towards a new game inspired by the KQ4 storyline? Seem unlikely, though.
Crucifix is a word I could imagine in the title of an Indiana Jones or even Gabriel Knight game. But I think both those series would be kind of dangerous territory legal-wise... given that Indiana Jones is still a currently marketed franchise, and also Jane Jensen still appears to be active in game design, and I don't think she'd be pleased with someone using her characters, which could make for an uncomfortable situation, even if she's not the one who owns the rights.
Finally, I come back to my earlier suggestion of
vortex. Having a vortex in a game would open up all kinds of possibilities for time and dimension travel. And, as I mentioned earlier, the word "vortex" is used three times on the "About Us" page for Infamous Adventures, the team with which MI is associated for other projects, but who apparently have no official involvement with this mystery project.