Between Light and Dark

"We already knew the mortal world. The world where human beings are living their joyous life. Even though the others have so many troubles. But, this world has something, that the mortal world didn't have. And that... you must do what the prophecy says."
"But I, I am not like you. I am something else."
With both sides in one creature, the life that has to continue living will experience a lot of pain. More than what human feels. The world, another world that is not visible to human's sight... will be distroyed for some reason.
The Darkness will slowly take the place of the light in the life, but one creature will... bring that light back.