Luna and Sombra grow close as they write one another over the years. Their friendship eventually poisons both of them. When such powerful creatures have relationship problems, everypony suffers.
A short, two-part companion story to The Assumption of Applejack, though it may be read as a stand-alone. It is an attempt at classical tragedy, so beware that the tone of the two fics is as different as night and day.
Original image credit goes to baisre on Tumblr and ikonradx of DeviantArt. The blame for the awful Photoshop job goes to me.