A world with magic, and a world meant to thrive without... Legend has it that six ponies would rise seal the rift between the worlds that were never meant to meet, returning harmony to both. And I, Twilight Sparkle, am the one destined to seek out these foretold saviors, these valiant heroes with incredible power, and together we shall save- Wait, wait, hold on... These are the ponies meant to save the worlds? Oh no. Oh, no, no, no ,no, no! We are doomed. So doomed. Celestia, help me.
Equestrian is home to many a powerful and magical creature, but not all get along. Feuds between the mighty caused havoc, and so it was that the great wizard Starswirl the Bearded opened the first rift to another dimension to banish the malicious. Little did he know that the continuous tears in the cosmos that occurred for centuries thereafter were greatly disrupting the natures of both worlds. Only a single thread kept them from colliding for many years, albeit a powerful one: The Elements of Harmony, for their power withstands in any world. Then they were tied to the alicorn sisters, and all seemed to be at peace. That was, until, the fall of princess Luna. Both sisters broke their harmony, and when one had to use the elements to banish the other they thus severed their ties to them. And so the worlds collided. When a world full of magic meets one without, they try to find balance. Thought they meeting of the worlds was a brief occurrence, much of Equestria's magic got swept into the other world... as much of is populous was. Now Equestria struggles to thrive under chaotic conditions left in the void meant for it's missing. And the other world? It now has magic not meant for it, muted magic that is constantly struggling against natural order. And in this place ponies are not the dominant species.
A thousand years after the collide, the elements have finally bound themselves to new bearers. All Twilight has to do is step into that other world, find them, return the lost magic to Equestria, and permanently seal the breach between the worlds. Okay, so it's not much of a plan, but at least there's a checklist!
IMPORTANT: This is my 'warm-up' story. That means I work on it about fifteen minutes a day before writing for an hour on one of my main projects. This story wont be as well organized, but it'll still be fun.