Following the Changeling Invasion of Canterlot, Twilight's friends, Princess Celestia and Shining Armor lament over how they failed to protect Canterlot from the Changelings as well for their behavior towards Twilight at the Wedding Rehearsal.
A dragon wanders into a land that banished him centuries ago. Never did he imagine he would return, but when the sun and moon failed to rise one fateful day, something compelled him to begin the journey home to the princess who shattered his heart.