Princess Luna disappears from Equestria with hopes of saving the world and is accompanied by the enigmatic Sombra. Meanwhile, Celestia tries to bury secrets as immortal as she is and Cadance must choose her loyalties carefully...
The code of the alicorn is that only those lucky enough to be born that way will stay immortal. Those who ascend have the same life expectancy as any other normal pony. ["Will you still love me when I'm no longer young and beautiful?"]