What happens when a unicorn with no magic by birth, gets possessed?

An ordinary human can do many things, there is no one thing that any human is exclusively good at. As such, a human can master many things in there short, insignificant lives, all with pure science. But what happens when you factor in magic?

Once Captain of the Royal Guard, Supernova quits in a fit of rage. Calling Princess Celestia a power hungry bitch in the process while defending Princess Luna.

Manticores. The most powerful animal on Equestria. Humans. The most powerful creature on Earth. Prophesies. The cryptic messages that tell of future disasters and heroes. All three are connected. Two have done terrible things. One will be the center.

I'm a Photophobic in a world of bright talking magical ponies ruled by a sun goddess.... What did I to in a past life to deserve this fresh hell?

This is a self insert story, the only difference is this is how I see myself if I wasn't a brony, and how I would like my adventure/arrival through/to Equestria to go if it were to happen with a realistic reaction to showing up in a new world.