A Diamond Dog king, feeling bold after gathering an army of 100,000 dogs, decides the best way to flex his new muscles would be to invade Equestria for past perceived slights. As such, he sends a letter to Princess Celestia with a declaration of war.

It goes about as well as you'd expect.

There was only one explanation. For all of it. All of the strange, erratic behavior. Her irrational fear of the sun. Her nocturnal habits of locking herself in in the dark and closing all the blinds. Wearing her sunglasses everywhere, even inside! It was time to invest in some silver, garlic, and a wooden stake.