Mirror Realm
Plot
Mirrors are more than just reflections - they are also doorways - to other realities. Doorways that should never be opened. These other realities are unlike ours. These other realms stretch behind the physical world, beyond time and space. Creatures that should never be allowed to crossover.
It's not what we see in the mirror that we should be worried about, it's what's behind the mirror looking back at us.