What point is there in peace when everypony that you cared about's freedom has been taken away and made into slaves?-Rainbow Sparkle/Empress Darklight

Officially engaged, Rainbow and Twilight decide to create a filly from magic, which they named Rainbow Sparkle. to their surprise, she resembles both the two, but is an Alicorn. to make things worse, a group of cults known as The shadow of slavery, whom are the followers of sombra, have plans for the filly. what are their plans? Are they planning something bad? Will Rainbow Sparkle be able to defeat her dark side? Or will she fall victim to it and make all of Equestria slaves?