You know I've been waitin' on the other side
And you, all you gotta do is cross the line
Being on the other side is a metaphor for being in the realm of stardom, fame, and fortune; the becoming of an elite and crossing the barrier that divides the normal citizen from those with power.
He has made the sacrifices it takes to get to this other side, selling his soul to the devil and therefore becoming a monster.
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