A foal walks up to his parents and asks:

How was the Crystal City built? The parents respond that, to the north, in the snow, there once lived a couple whose love knew no bounds. Then one day an evil sorcerer came and demanded the couple submit to his will. The couple rejected his offer and fought back. In the ensuing battle, only one stood, her husband dead and the sorcerer gone. The mare, heartbroken by the loss of her husband, tried to join him in the afterlife. But before the sorcerer left he placed a terrible curse upon the mare in revenge that she may never die unless she builds a city for her husband out of a small crystal that only forms every 100 years at the peak of the highest mountain of the land. And that when the mare has completed her task and the city is built the curse will be broken, and that she may be with her husband once again for every second of Eternity there ever was and ever will be.

This was basically a self-imposed one-day Oneshot challenge. So your milage may vary but please do enjoy the horse words I have provided