What if Spike hadn't ventured with Twilight? Well, a much different story would have been told.
After opening King Sombra's door to her biggest fears, Twilight Sparkle never returned to save the Crystal Empire and was never heard from again. Within her vision, her fears consumed her. With everything stripped away from her, she slowly became corrupted and began to follow the footsteps of King Sombra within the shadows.
Twilight's Vector can be found here: [link]
King Sombra's Stained Glass Vector is by [link]
All editing was done by me.
Here's another great piece that is very similar to this one!