The 7th element: MLP(my version)

Honesty, kindness, laughter, generosity, loyalty and magic the 6 elements of friendship that we all know and love that have helped keep Equestria in perfect harmony for many years. But when a new threat comes to Equestria the main six learn very quickly that their six elements aren't enough to save the day, not this time. In a desperate act to find a way to fend off this new threat twilight learns of a seventh element of harmony that has said to be lost and the pony that is said to wield it that once lived in the crystal empire. The six are skeptical about the strength of this new soon to be Ally until they learn that she is the lost princess and true ruler of the crystal empire... Who is this mysterious pony? What is the seventh element? And will it be enough...... To save Equestria?

You'll have to read to find out