A short time after Princess Twilight Sparkle and Prince Galleon were married, Twilight conceived and Delivered a little alicorn Filly. The two named her Harmony after the Elements of Harmony. A few weeks after Harmony's Birth Twilight and Galleon went missing, Twilight was found dead in the everfree forest her wings broken and royal attire shattered around her body. After weeks of Searching Galleon still wasnt found, and it was assumed he had come to the same fate.
Celestia took in the young filly and raised her as her own, after Twilights death her friends decided to move to Canterlot and with them came their families and their foals, Harmony quickly befriended them.

Now Harmony is being mentored by both Celestia and Luna, and as thought she is more powerful then both her parents combined, its starting to show, but with it comes the threats on her life and the lives of the ones she hold dear.

Harmony has a younger sister that she has no idea exists. Night Wish but the younger alicorn wasnt so lucky, she is being raised by the Vilan that is trying to take her sister from Canterlot.