They become immobile in the real world as their mind/spirit are in an alternate reality. He wouldn't die as he'd likely be left alone at that point, and he can't die of old age as I recall, but it would likely be a victory through incapacitation. Course, he'd only break out the labyrinth once Lelouch started homing in on AS's pocket universe, before that it'd just be Mugann (which would do **** all to Lelouch IMO), and the planet buster anti spiral creations.
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MMBN style fighting game made by me in the link below!
http://sandbox.yoyogames.com/games/184947-b8bn