The Shaper is a smith of unparalleled skill, her creations the most sought after in the fallen world. When a pony named Lyra comes to her with a unique commission she has to put all her skill to the test to craft a weapon of great power. For Lyra's goal is not an easy one, and it is not just any weapon that can kill a Dragon.

A story inspired by this and this image, as well as this challenge by CDRW (whose fic A Still More Glorious Dawn Awaits is quite good).