In this story, Cozy Glow locks Twilight Sparkle and her best friends Rarity, Applejack, Pinkie Pie, Rainbow Dash and Fluttershy in a room, leaving them no choice but to participate in her twisted game in which she manipulates them to bring out their dark side and fight to the death. I recommend you read this story in dark mode. It adds to the creepiness, for those who want that ;)