For Contest

When I first read this, I immediately came up with ideas. First of all, she already has an amazing ability, one that allows her to travel between the present and the future. Work on it, expand on it; make sure to try to explain how she got the ability and how it will grow and change, if at all.1

I was thinking that maybe he kept her because he was well aware of her gift...because she is originally from the future. Her parents were leaders of the resistance before the demonic lord began taking control. He went around dominating everyone, killing the females because he learned that a human female would be his downfall. Her ability is matriarchal and is passed from mother to daughter and so on.2

Her gift stems from the Earth and the Fate, who in this case is in the flow of time and controls the destinies of everyone and everything. It includes more powers as she grows older and such. You can pick what powers she will get. 3

He didn't "spare" her; she saw herself in the future realm because she will end up there...it's the whole time paradox thing. 4

I'm sure you can develop it from there.