Twilight and Rainbow Dash have a sleepover at Rarity's. However, once the bitter winter chill sets in at night, Rarity unveils to her friends her new line of sleepwear fashion that she's sure to keep them warm.
After her cousin, Duke Blueblood, deals a successful coup and takes over the kingdom of Soothsay as its new king, Princess Rarity sells her very being to a demon.