Twilight Sparkle, now the Princess of Friendship, focuses on proving to everypony through the adventures of Season 5 of Friendship is Magic onwards that she truly has redeemed herself for her past actions as Midnight Sparkle.
Twilight Sparkle is gone after tragedy has befallen, in her absence a new unicorn comes to town but is secretly up to no good as she has a hidden agenda and a mysterious motive up her hoofs.