Princess Celestia is widely regarded as a kind and wise soul. So what could cause such hatred in her for the Human race? Perhaps, she merely seen something best left undiscovered.

This story is a one shot. Not some overarching story, merely an origin story of sorts on what could cause the Princess to become so hateful from humanity. In this case, it was the fact that she ended up, not on earth as we know it, but the earth of the Cthulhu Mythos.