Background Pony #5879
So it is only a “rediscovered tribe” that came from the early Crystal Empire - the pictures of the buildings suggest that this is a settlement of recent date. Crystal ponies with horns have not been seen in the TV series of G4, but in the comics - especially Radiant Hope - it has been seen that these existed back then. These form a small minority in a poorly known society because the crystal ponies and the umbrum had a mysterious relationship with each other.
It is possible that the Wishing Star will appear in SoS, as the light shows in the sky as the music played showed a star that undoubtedly looked like the Wishing Star. There are quite a few star symbols, most based on Twilight’s cutie mark and power symbol which are two different marks. So the New Mane 6 and the crystal unicorns celebrate the same thing, the Winter Wishday.
Nothing to suggest “secrets” so far. 100% G5 lore.
It is possible that the Bridlewood unicorns had contact with these crystal unicorns, as it is possible that Misty’s mother may have been from this tribe - the design of her horn is unusual. All bridlewood unicorns have long and symmetrical, sharp horns reminiscent of those the Canterlot unicorns had in the previous generation. But Misty from the very beginning has an asymmetrical horn that is angular in several places. Not as angular as the horns on these new unicorns.