In a humanized variant of the MLP universe, there are Mages, Nephilim, and Sapiens. The fourth race are the god-like combinations of all three races: the High Bloods. (Celestia, Luna, and Cadence.) However, a fourth High Blood has arrived on Earth after a crash landing. His name is Prometheus, Prince of Fire, and he has broken out of his ancient exile to warn Celestia of the inevitable return of her long lost "siblings". Now, it is a race against time as Celestia prepares the Bearers of Harmony to discover the Element's final purpose as the ancient gods escape their prisons, one by one. Lines will be drawn. Love. War. Insanity.
Celestia's past will be buried no longer. (MINIMAL chance of gore later, checking off the "Gore" box just to be safe.)