One day when it is raining heavily outside, Twilight decides to raid Spike's comic book collection and play a while as the Power Pony, the Masked Matterhorn.
She finds herself in the story of how one of the most dangerous villains in their Rogues Gallery came to be. Spurred on by Matterhorn and molded by the Mane-iac, this new villain is unlike anypony Twilight knows how they came to be opposing her.
Art done by EuropaMaxima on deviantart.