Two alicorn fillies, one with a coat blacker than the night, and one with a coat lighter than snow. The princesses believe these fillies to one day inherit all of Equestria, along with the task of raising the sun and the moon. Alas, not everypony has good intentions for these two girls. The same spirits that helped create Nightmare Moon have their sights set on the twins, and this time, failure is not an option.