Celestia and Luna thought they killed off all the black and red alicorns eons ago. Sadly, they were wrong. Dead wrong! Now, an army of the insufferable things are poised to strike and they have to do something about it. Thankfully, the Sunshine Smiles space marine chapter, the least respected of all the imperium of man, are passing by and are more than eager for a good xeno purging. For the Emperor!
Obvious Warhammer 40k crossover. You know, 'cuz there aren't enough of those already.