The Cutie Mark Crusaders, frustrated with their lack of success, begin searching through Twilight's library in an attempt to find out more information about cutie marks themselves in the hope that they will finally understand the way to get their cutie marks. However, the trio runs across an ancient book containing evil spells and they attempt to get their cutie marks in the worst way possible...
Cover art by http://sniper-bait.deviantart.com/
Now with its own TV Tropes page! http://tvtropes.org/pmwiki/pmwiki.php/FanFic/TheCutieMarkCrusadersBringAboutTheApocalypse