Wicked Prince of Mirrors: A villain gets the girl romantasy

Once upon a time. . .

there was a prince so vain, he collected mirrors to preen at his appearance. He gathered them from across the kingdom, mirrors of silver and gold inlaid with crystals, carved with marble, framed in sculpted filigree. His collection turned into an obsession. He had no care for his people and funneled their labor, their coin, into a shrine for himself, a kingdom of silver mirrors and gleaming glass.
The citizens of his kingdom grew desperate, for war pressed at their borders, creatures lurked at their doors, and famine broke out. But there were no armies to fight for them, no king to protect their land. 
Someone so selfish, vain and careless should not rule, so the people plotted to overthrow him and put an end to his greed. They marched upon the palace and called for the prince to come forth.
He did, but when he saw their treachery, a madness overtook him and he summoned something terrible from the mirrors—a monster that would reflect every evil back on the people. Before it could strike, a sorcerer stood up and cursed the prince. 
Every mirror he looked at would shatter, and he’d never see his reflection again because he’d be trapped behind the glass, switching places with the monster he’d summoned. He’d live out his days in the mirrorverse until he learned his lesson. 
As for the beast, the sorcerer let it escape. . .