Princess Twilight Sparkle is recovering from an attack from her star pupil aka Starlight. Starlight stole Princess Twilight Sparkle's wings. Starlight surgically attached Princess Twilight Sparkle's wings to her back. Rainbow Dash had told Princess Celestia what Starlight did to Princess Twilight Sparkle. Starlight is restrained in the dungeon of Canterlot Castle. Princess Twilight Sparkle's new wings are crimson. The mysterious donor of Princess Twilight Sparkle's new wings is unknown to all ponies since the donor was wearing a cloak when they donated their wings. Starlight has mentally snapped which is why she stole Princess Twilight Sparkle's wings and Starlight in her mind thinks that she'll be a better Princess of Friendship than Princess Twilight Sparkle. Princess Twilight Sparkle is more commonly called Twilight since she likes not being called Princess when she isn't busy with any royal duties that she may have to do.