The Phantom’s lair underneath the opera house was dark, cavernous, and candle-lit. This was a place that no one else could get to, a place where the ridicule and hate that had followed him all his life could be left behind.
In the corner, a piano where he would sit and compose symphonies and operas that would most likely never see the light of day. Maybe there was a bright side to this dark cave, all those hours alone in the dark refined his love of music, he made Christine the best singer in the opera house.
In those walls, the resentment that the world had given him grew into his anger that he reflected back onto the world. The cave was a place he could dream of better things. He built the dual thrones for himself and Christine because he wished for a companion. His lair was a place to pretend. It was a place where he could leave the woes of the world behind him.
His lair was a place he could plot and plan, where no one would find him. Yet this same haven also trapped him in his misery and sadness, which eventually hardened into anger.
His lair was not a happy, not welcoming, and everyone who descended with him was frightened away by this dark place. This is a place for the Phantom to hide from the world that gave him naught but hate, fear, and resentment.
It was a place that he could be alone with himself, the only person who accepted him the way he was.