Princess White Flare’s sister, who once was an evil princess in the world of mortals, is now the princess that many ponies call the “ghost” princess. Not for her appareance, but for her haunting, terrifying past and her wish to eradicate the pegasus race.
 
Her parents, Queen Galaxia and King Cosmos, judged her actions fairly after she passed away. Because she wanted to destroy the entire pegasus race, she lost her wings and because even if she was a divine alicorn who had an important role in the universe, her wish to expand her empire, known as “The Sirian Empire” and eradicate other pony species was unforgiveable. In consequence to her actions, she cannot open her eyes and cannot see the beauty that once upon a time, she wanted to rule. Even if she can’t see, her immense hatred left her soul when she had the last fight with Princess White Flare and Princess Luna, leaving nothing but a pure, positive, genuine and unclaimed smile on her face.  
Stellar Flare always thought that unicorns were the only race that deserved to exist along with earth ponies and the race that she used to rule, the “ponies of the dog star”, better known as “the sirian ponies”, an hybrid unicorn sub-species known for their long white manes and big horns. She has been banished to her own star, Sirius A, by her own sisters, Princess White Flare, the princess of Sirius B and co-ruler of The Sirian Empire, and other two sisters, Princess Celestia, princess of the Sun and Princess Luna. princess of the moon.
 
Those who love her say that she was a fair ruler and an actual princess who wanted the best for her empire of unicorns. They also say that she helped with the creation of the elements of harmony indirectly, by making her sisters do things that nopony did before… but those who hate her say that she was the most cruel princess in the story of ponykind and that her hatred spread all over Equestria after she passed away.  
Nopony knows the truth for sure. Only two living sisters in the solar system know the truth about her. Stellar Flare is a memory from their past. A past that surely the now grown princesses don’t want to remember.