A few nights later, Luna has a nightmare she hasn't had in awhile, the nightmare of her and Celestia's mother and father dying at the hoofs of the evil unicorn Matriza. As the nightmare continues, she begins to call and Celestia and Twilight come running. "What's wrong, sister?" asks Celestia as she shakes Luna awake.
"It happened again, I dreamt of mom and dad dying at the hoofs of Matriza, it's the worst nightmare of them all," Luna bursts into tears and Celestia sits down and takes her little sister in her arms.
"Wait, what? I've never heard of any Matriza," says Twilight confused. "Who was she?"
"The ancestor of the pony you know as Prismia, the pony that Cadence stopped to get her wings. Matriza was Prismia's great great great grandmother and was just as evil, if not more than, her great great great granddaughter," explains Celestia still trying to console Luna.
Twilight then bows out and goes off to her studies for the night. She wants to do a bit more research of her own on this pony known as Matriza and how she was able to take down two full grown alicorns on her own. In the library, Twilight scours through every book until she finds the one on Dark Magic and Its Users and on the top of the page is Matriza and right under her is Prismia. As she continues to read the book, she also stumbles across a familiar name: Sombra. She then flips to the page with information about Matriza and begins to read. "Matriza was the prized pupil of King Sombra while he was still alive. She was his faithful student and even took up the dark arts and dark magic after his banishing. With her newfound power, she went and confronted the most powerful creatures of all Equestria: the King and Queen of the Alicorn Kingdom. She then killed them as their daughters watched on from the sidelines. But still having a little bit of heart left, she couldn't bring herself to kill the little fillies." Twilight continues to read. "After having killed the King and Queen of the Alicorn Kingdom, Matriza returned home, satisfied with her accomplishment. Until her, no other unicorn was able to take down two full grown alicorns on their own." Twilight then closes the book. "Wow! No wonder Luna is having nightmares about this pony killing her parents. This pony was powerful, by the looks of it, extremely so." Twilight then goes off to her room in the castle and falls asleep after all that research. She's tired. She's also glad to know a little bit more about why Luna is so scared of this unicorn and her descendants.