The Techno-Monks were attempting to formulate a summoning spell for bringing far off objects to a location without having to use portals. The first test of them, had an unforeseen side effect. It did not have a correctly binded target and that made the magic go haywire. The thing that was actually summoned was a gray equine with a blonde mane and 'derped' eyes.
"Hey! Trixie! What's the big idea with the teleporty-switchy again? I thought we were done with that... Ooh! This is Mr. Ghosty Knight's castle!"
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Sable was investigating the monks newest invention, the multiversal disturbance radar. Oddly enough, a disturbance had occured in two places, an odd looking desert-ish place, and in the lair of the Techno-monks. "They must have bungled something incredibly badly this time.'
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Derpy had already pushed most of the buttons she could find, knocked over many potions (Setting back much of the monks research by at least 3 years) and flown into two walls. She can see out of one of her eyes a new visitor. "Hi Mr. Ghosty Knight! It looks like you're still here! I thought everyone had gone when she came..."
"Small equine, what is your name, how do you know of my island, or me, how did you get here, and who is this she?"
"You don't remember me? I'm Derpy Hooves! Eqestria's mailmare! Wait, this place looks a bit different... I must be in the past! Ooh neat! Now I can tell Twilight I've been to the past too! Oh, wait, I remember some sorta warning she gave me, let's see, "Don't... rewrite... history... Don't... tell... the past... its future." Ooops. Uh, just forget about what I said earlier, can I go home?"
Sable starts leading the curious pegasus to the portal and starts contemplating the other anomaly. Derpy leans over to the portal frame and pushes a button. The portal activates, it's destination, dictated by Sable's thoughts, is the desert. Sable realizes what's going on and attempts to stop Derpy from entering the portal, knocking both of them in.
"Well Ms. Hooves, this certainly an interesting predicament you've blundered us into this time."
"I just don't know what went wrong"