With the Barrier slowly consuming the Earth, and nowhere else to go, the population of the world has little choice other then to go pony, or die.

All but one who finds himself unable to go pony. Instead the potion renders him immune to the Barrier and magics toxic qualities, as well as giving him the ability to use magic that isn't toxic to regular humans. Exposure to more potion won't force a transformation either, only increase his magical prowess...

He stands alone. The only human who will survive the Collision of the two worlds...

...Then again, screw destiny.