Rarity's been hiding a secret, even from Sweetie Belle. And it makes the least sense of all, because Rarity hates getting dirty. Because it least of all makes sense to her friends. A Space Marine is designed to keep the Imperium from falling, but Rarity, she protects Equestria from harm. And it's pretty hard keeping that from her friends.
This is the first story of a "mini" series of the Mane six in a Warhammer 40k setting.