For countless years, Celestia and Luna have ruled Equestria, guiding ponykind as their ancient father, King Solaris, would have done back in the golden age of their people. But now, with their retirement upon them, the two alicorn sisters decide that the time has come to finally undergo a plan they have been discussing for some time. The return of their lost predecessor.
As one might expect, this went swimmingly for everypony involved.