This MLP AU centers around the Great Crystal War between King Sombra and Queen Celestia, where it was eventually won by Equestria, but not without great cost and devastation.  
Queen Celestia, Luna, and Cadence were killed in the War when Prince Solar Radiance and Prince Orion were only teens, thrusting them into a kingship that neither was fully ready for.  
King Orion Sparkle(formerly Prince), is the son of Twilight Sparkle and Sunburst. He is the ruler of the dusk. Witnessing the sudden deaths of both his parents shook him to his core and, while he was a rude, arrogant, and anti-social prick before, he is even moreso now. Being thrust into sudden kingship made him pour over hundreds of texts from the Royal Library night after night, foregoing sleep and meals for fear of letting down his subjects, but most importantly, letting down his mother. It would have killed him if Solar Radiance, yet again, hadn’t stepped in with the entirety of the Canterlot army storming the halls and forced him to take a break.  
Personality: Orion is a short-tempered unicorn, quick to argue and always the last to back down from an argument and admit he was wrong. His heritage to Princess Twilight got to his head and made him arrogant and snobbish, unwilling to mingle with the ‘commoners’ and instead draping himself in the solitude of the night. He detests stupidity, children, and the lazy and weak. While part of his personality resulted from his mother’s excessive praise and coddling, his heart only hardened after the attack on Equestria.  
Special talent: Unlike Solar Radiance, Orion is extremely talented in magicmaking and casting, perhaps to the level of Princess Celestia herself. Of course, this was a natural result of his workaholic attitude and months spent pouring over books. He is also talented in potionbrewing, and has even invented a few spells himself.