Now I'm sure you're aware that The Hub had let us see a clip from Comic-con [link]

well considering the fact the crystal ponies have muted colors compared tot he mane six and flat hair comparable to Pinkie's when she's sad. I assume that the the ponies are basically as sad as Eeyore and deduce that the Crystal fair(e) is meant to cheer them up. As for King Somber i assume that he will be the villain (obvious statement is obvious) But not the only one. The crystal ponies were not aware that they have not disappeared a 1000 years ago and one commented that it "feels like yesterday" Also note that according to the map there is a place near the Frozen North call the "Crystal Mountains." I believe that the empire will appear there. For those of you not familiar with cryonics (what people commonly mistake as cryogenics) or at least the begging of Futurama. Cryonics is (Quote:Wikipedia) "the low-temperature preservation of humans and animals who can't be sustained by contemporary medicine, with the hope that healing and resuscitation may be possible in the future." in a process called "Cyroperservation" Note that at this point Cyroperservation if irreversible with modern technology. But this speculation is about a word of magical talking ponies of that part is irrelevant. You might think that this talk of cryonics/cryogenics is all irrelevant but considering the placement of those mountains and the facts that A) The pegasi can make snow fall and B) There a canon type of monster know to freeze the inhabitants alive, The following scenarios seems likely:

1) 1000 years ago perhaps in the midst of Discord's chaos. The climate went to subzero hell and froze the Crystal Empire.
2) Somber was (and probably still is) a hateful stallion and might have attracted the Windigoes to the kingdom and froze it over.
3) Several pegasi were in charge of winter. They then neglected their duties, accidentally froze over their sector (The Crystal Mountains and Empire in this case) and forgot about it.
4) The Empire was frozen over near where the first leaders founded Equestria (1000 years seems more of an estimate when you think about it)

Granted all these scenarios would have involved the Crystal Ponies surviving the accidental cyropersevaton but we know little about these ponies so surviving being frozen in a prolonged ice age would be in the realms of possibility. in fact if there were cyroperseved by accident chances are they would not have <a href="[link]"<Cyroprotectant solutions they the cells would die due to freezing. That pony Twilight talked to said she didn't remember anything before Somber's rule. And I'm pretty sure that without brain cells your memories would fade. (Among other things)

EDIT: mentioned that the eyes that appeared in Twilight's scene resembled King Somber's and that a black pony appeared on the Hub"s Wedding quiz game that looks like him. Bringing forth the possibility that he may have been be corrupted like Luna was.

EDIT 2: apparently the new villain is called King Sombra.

Conclusion: The Crystal Empire was frozen in a self-contained ice age. Most likely under scenarios 2 or 4 (and to a lesser extent 1) And the Mane 6 are putting together this fair(e) to ether:

a) Help the Crystal Empire remember the culture that was lost when Somber took the throne. or
b) Cheer up all the depressed ponies in the empire (and there seem to be a lot of them)

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