Twilight is corrupted by exposure to dark magic, and Celestia traps her in an extra-dimensional space called 'The Light Prison.' The Seam is a tear in space that is the exit to the Light Prison, but is usually invisible because the only thing that exists there is light.

A short story I wrote in late 2012 to accompany this piece of art I made. Yes, I drew the cover art. You can find it on my dA page here -- im-not-sue. Also featured on EqD drawfriends 653, #41.

This inspired me a little, when coloring -- link
It would be appropriate listening music, I think.

I have always been alone in this forest. I have always feasted in this forest. I call this forest home and those ponies that travel through it are my prey. I devour all those who fear me, all who come to face me. They fear me for I am Fear incarnate. But now...I have met one who does not fear...and I am unsure of what do with her...

Image by the very awesome thewraithofwolf

Several days after having a terrible nightmare, Scootaloo takes her final exam at the Cloudsdale Flight Academy, and with the help of Rainbow Dash gains insight into the nature of her own character as well as knowledge of the deepest secrets of the Rainbow Factory.
Upd: YouTube reading by linksbro1: link