For every Corrupted Cutie Mark Crusader defeat, somepony always show up to stop our heroes from curing them, and that somepony is Diamond Tiara. She appears out of nowhere, thank's to her Tiara's teleporting magic that came from Discord, and mpck and insult our heroes for being too slow, stupid, ignorant, and clueless. She's convinced that she will rule alongside Discord, with those three "Blank Flanks" as her slaves. She then warps each of the Cutie Mark Crusaders away, but before she leaves, she says that if they want to save Spike, they must travel to the changeling Kingdom!
Actual Music: Now He's Playing Clasical Music from Portal 2
Artwork: Minimalist Wallpaper 38: Diamond Tiara by *Softfang: http://softfang.deviantart.com/art/Minimalist-Wallpaper-38-Diamond-Tiara-287161497