Captain Vestus Benedicto, a recently renegade Space Marine from the Mantis Warriors Chapter, is torn. In the aftermath of the Badab War, he and his men feel that they will never again be accepted. As they travel far beyond Imperial space, they encounter an...interesting planet. After travelling into the Gheist Rift, they find the strange planet of Equestria, as the Marines of the Mantis Warriors try to adjust to their new neighbors the discover that they aren't the only ones who seek Equestria. As vile Dark Eldar of the Kabal of the Ninth Tide invade to torture and abduct the ponies of Equestria, the Mantis Warriors prepare to defend their temporary home.