I have recently come up with a story of the Alicorns rising and fall, and their connection with the evil Ram Necromancer, Grogor (still hoping he could rebooted into the series).
Long before the founding of Equestria, there were the three pony tribes: Earth Ponies, Unicorns, and Pegasi. But unknown to most, there was a fourth tribe: The Alicorns.
The alicorn are the most powerful out of all of ponykind. They would be workshop as deities and offer themselves with their lifelong passion to serve the other tribes. They would help the earth ponies nurture the land and plants, aid the pegasi to manage the weather, and teach magic to the unicorns. Like other ponies, each of the alicorns are gifted to perform their various duties. For example, some alicorns use there magic to control the sun and moon. During the time, Celestia was just a filly who hasn't discovered her purpose just yet, and Luna was merely an infant. This master race would maintain the balance and harmony between the three tribes. It was a golden age. But like all golden ages, it was brought to an end.
One fateful day, the alicorns were challenged by a being of great power, Grogar the Ram Necromancer. He was a master of the dark arts, blessed with a magic of his own. In his quest for conquest, his power grew in his practices, along with his hate, his malice, and his will. Seeing how the ponies used their magic and lived in prosperity, he declared war on all ponykind. But there was one thing that stands in his way, the alicorn. So he began his onslaught by eliminated the alicorn. Grogar's magic was already so eminence, he had no difficulties at overpowering alicorns. One-by-one, Grogar hunted and destroyed the once great master race; all expect for two.
Celestia escaped with Luna from the destruction of their people. Grogar was able to track them down and corner them them. Before he could destroy them, he was held at bay by a loyal subject of the alicorns who come to their rescue. The young unicorn wizard, Star Swirl the Bearded. His magic was just as extensive as Grogar. The two clashed in a massive battle where they nearly destroyed each other. Star Swirl was able to defeat the necromancer by setting a trap with the aid of Grogar's unwilling servants. They managed to seal him away, ending his senseless madness. Star Swirl then took it upon himself to take in and protect Celestia and Luna until they were ready to take their place. From that day on, Celestia vowed to uphold her people's legacy, and protect and serve her subjects.
Without the alicorns, the balance between the three pony tribes would slowly crumble. It didn't take long for the ponies to start learning hatred. And that is when the Windigos came.
The Legend of The Alicorn Tribe and The Ram Necromancer have faded over time. No one remember the truth about that time; except for Celestia, Star Swirl, and the lord of chaos, Discord.