It is rarely known that during the forming of Equestria as told in Hearth's Warming, the Equestrians faced threats from all sides by those looking for conquest. But, In their hour of need, the Cydonians of the Southern Continent came to their call. In exchange, an immortal treaty was signed between Celestia and their King, Saladin. The Cydonians would defend Equestria against all threats. In exchange, when the Fourth Alicorn to ascend became of age, they would be betrothed to their Firstborn Prince.

That treaty was signed nearly 1000 years ago, and Celestia thought nothing of it, until a Cydonian Fleet appears in the waters off Canterlot, having heard of Twilight Sparkle's Acension and Coronation. They intend to have the terms of the treaty fufilled, and nothing will be the same. For Twilight Sparkle, Celestia, or the Elements of Harmony, and the Cydonians.

What will come of this? Only time will tell...
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Will have implied an implied sexual relationship, with some AU elements. This story takes place six months after the defeat of Lord Tirek.