The Disc World?

A world shaped like a disc is what you saw in your dreams. With one side pointing a star called Cephei and the other side pointing at darkness. The mystery of this planet is very high and the species that lived there would have opposites on the other side. The dream goes on fast-forwarding itself revealing how the world develop, how they go into war and ending it, how it all changed.

An indistinct yell came from nowhere and all sudden, it was pitch black. Objects like a sheet of paper, quill and other medieval ages objects came together and formed a picture of someone signing something. A treaty it seams, both the dark and light side of the world was populated with opposite species. Dark species live in the light side, species opposite to the Dark species live in the darkness.

The Dark species includes vampire bats, banshee, grim reapers and etc. Meanwhile the opposite of them may be found normal to you. And then, it was pitch black and you can hear chatting, but it was quiet like you were closing your ears and slowly opening them. You woke up in a room with a vampire bat talking to another vampire bat, as the other one leaves the room. The previous vampire bat approaches you trying to help.

<The fate of the story is in your hands now>