I don't know why I'm here... But here I am... I have to start a new life... Turn a new leaf... I don't like to fight... But if it's what I have to do to save the people of the country that took me in, then so be it!

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I'm not sure if this abides by the rule of having to be relevant to the Friendship is Magic universe, but I'll give it my best shot.

Rainbow Dash remembers her parents saying that a mark on the bottom of her right front hoof would appear, only when her sibling is in Ponyville. When Mahogany Cloud finds out that he has a sister, things go out of their way to make it trouble for everyone.