Twilight has discovered a new power though she is unaware of what type it is. Before she can truly being experimenting; another evil begins destroying Equestria. With all options exhausted Cadance, Celestia, Luna and Discord send Twilight to an alternate dimension that may have more resources to help them fight this new big bad.

Now Twilight must deal with a younger Celestia and Luna, attempt to control random bursts of her new power and deal with a curious Spirit of Chaos while also completing her research.

Discord decided to get involved. Is there any other explanation needed?