THEORY: in reverse order, the events, we go back to where we started at the very beginning...
Lotto: EXO are escaping the game they’re playing in the casino with a girl Lucky one: Only EXO were caught and they started performing clinical experiments on them Monser: EXO becomes monsters after receiving the clinical treatment Sing for you: EXO are singing a song in reminiscence of the girl Love me right: EXO are starting to develop hallucinations from the experiments EXODUS: Attempt at escaping succeeded Overdose: EXO gets caught once again and they get locked in a maze MAMA: At the end, they gathered their force together to return to their original form Source
When the skies and the grounds were one, the legends, through their twelve forces, nurtured the Tree of Life. An eye of red force created the evil which coveted the heart of Tree of Life, and the heart slowly grew dry. To tend and embrace the heart of tree of life, the legends hereby divide the tree in half and hide each side. Hence, time is over-turned and space turns askew.
The twelve forces divide into two and create two suns that look alike into two worlds that seem alike. The legends travel apart. The legends shall now see the same sky but shall stand on different ground, shall stand on the same ground but shall see different skies. The day the grounds beget a single file before one sky in two worlds that seem alike, the legends will greet each other. The day the red force is purified, the twelve forces will reunite into one perfect root a new world shall open up.