For Luna, becoming an alicorn was a choice. Unlike Celestia, she was given a choice about whether or not she would die to save her people.

Luna was Celestia’s first student, as a filly, she showed the rare skill of dreamwalking, and the even rarer gift of prophecy. She would predict unexpected changes in weather, or the yield of a harvest, receiving the information in vivid and often frightening dreams. Celestia wanted the young pony’s insight, and took her on as a student, hoping to teach her how to better understand her visions, and perhaps use her dreamwalking to help ponies in need. Things went well for many years, well into Luna’s adulthood. The two mares were very close, sharing an almost sisterly bond.

Celestia cared deeply for Luna, feeling like the young mare could fill the hole in her heart left by the foal she lost all those years ago. So when an opportunity arose to immortalize this surrogate child, Celestia leapt at the chance. Luna had a horrible vision of a great falling star crashing to the earth, killing everything in the great crater it would make. After consulting with many astronomers, Luna’s prophecy was confirmed. A distant star was slowly growing larger on the horizon as it hurtled towards their planet. From the calculations of the astronomers, they had only days before the impact.

Luna and Celestia did not tell a soul, figuring that if they could do nothing, it would be best to not upset their people with such news. The two stayed up all night for two days, planning and trying to understand how to execute their plan, for Luna to fly into the falling star and give herself up to it, destroying the star and becoming an alicorn. Their plan was flawed, had no basis in any reality, and if it failed, everypony would die except for Celestia. But they had no other options.

In the middle of the night, mere hours before impact, Luna hugged her dear friend Celestia goodbye, gave kisses to her sleeping parents in their beds, and took off into the night sky. She flew hard and fast, her own form becoming like a shooting star itself, her silver mane flickering in the starlight. When she entered the stratosphere at last, and collided with the star, she felt nothing.

Her transformation was numb, and lonely, disintegrating into a thousand flecks of silver dust. She glowed like the hot, blue flames of a forge-fire, expanding and pushing all mater away from her new form. For a brief moment, she and the star were one being. And then that moment ended, and she was falling back to earth. With her new, alien body, she lit a horn that still glowed with white heat, and crushed the star into a beautiful white marble, the moon.

When she landed in the sea, far from her people, she felt different. She felt the ebb and sway of the sea, the pull of some distant force deep in her bones. When she looked up into the sky she always knew, one of inky blackness and distant stars, she saw her creation. Her moon, a silver-white ball, shined down on the planet, light dancing on every surface. She loved it.

When she arrived home, there was no fanfare like in the myths of Celestia’s birth. Only the rising sun, and Celestia herself, there to crown her as Sovereign of the moon, and co-ruler of Equestria.