Equestria’s newest baron has just discovered that his new barony is entirely underwater, his new castle is a broken-down old riverboat, and his new subjects are… seaponies. Welcome to the Barony of Fen.
Crossover between XCOM: Enemy Unknown and MLP. Twilight appears on Earth, shortly after the alien war. How will she cope with being taken prisoner? How will XCOM cope with the single most powerful psion they've ever encountered?