The Crystal Empire is not as sweet and innocent as they claim. It's an empire shrouded in darkness and sordidness. King Sombra is alive, and he wants revenge. When Equestria finally learns about the Empire, they try to help. Scarred by the cruelty of the Crystal Ponies, he isn't willing to accept their help. He wants retribution for what the Crystal Empire did to him and thousands of others. Whether Equestria helps or not, he will get justice, and there will be blood.

Unable to stop him, the ponies of Equestria try to show him another way. It is easier said than done.

And the Crystal Empire isn't the only mystery that will be solved...