So I have a conspiracy: the Earth Pony Crystal is actually the remains of the Crystal Heart, and the mysterious new villain is actually a corrupted Radiant Hope, judging by the respectively resembling appearances. And by'It's time to take back what is mine' she means that take back the Ctystal Heart and restore the Crystal Empire. Plus, funny fact, an official merchandise of Sunny last year had the description as 'Sunny is the main character of the last generation of My Little Pony. She's an Alicorn who plays a pivotal role in saving Equestria from King Sombra and his minions.'