The dark soldier could possibly be like kind of like a sepheroth to MX, except he is not as strong willed and determined as CLoud thus he gives in to the dark side of himself. When he gives in, DS could possibly "Take over" MX's body and forces him to use his power for evil.
Thus the true villan isn't MX, its the DS
Thoughts?
Thus the true villan isn't MX, its the DS
Thoughts?