"The world was our teacher, and its people were our charge. We shaped the land like clay to suit the vision granted us before time itself, and we erected our cities to safeguard the world's children. Life was good then - the sun shone warmly and we felt the light of the heavens so near to us. Ah, but that was long ago. These are legends to most of my subjects, but I remember those days as if they were moments ago."
- Princess Celestia
Alicorns were an ancient, immortal, and ancestral race of equines who originated on the planet Demeter in the universe known as Lenor. They are the progenitors of common modern day Equestrians like the ponies, pegasi, unicorns, and hippocampi. All alicorns are said to be children of the spirit Lenoren, who came from the heavenly realm of Aetherius and created them in her own image.
The alicorns ruled a massive and powerful, yet peaceful empire, which spanned their entire planet. Their empire came to an end after the Hundred Years War, in which the forces of Chaos brought about its ultimate collapse through a destructive civil war. Since then, only two alicorns remain in Existence, the reigning Princess Celestia, and her sister, Princess Luna.
The Alicorns were a primordial and ancient race of "Lenorians" were first created by the Eternal Empress Lenoren, daughter of the divine god Anurel. These ancient beings were the first civilization to ever arise on Lenor, an empire undoubtably the greatest that will ever come to be in that realm. These tall and elegant beings have a single horn, large graceful wings, and the most unmatched beauty in all planes of Existence. They were avid worshippers of the Divines, and had a flourishing society with an unparalled understanding of magic, athletics, science, mathematics, architecture, music, and many other topics of knowledge, now lost to the sands of time. The Alicorns built and resided in massive, beautiful cities throughout their empire, which expanded the entire length of Equestria and its surrounding territories, spanning the breadth of the entire world.
Not much history is known of the ancient Alicorn Empire apart from what was stated above. However, it is known that the Alicorns had an immense and powerful empire that ruled over the lands of Demeter for many millenia. However, this too, came to an end.
An extra-Existential force known as Chaos saw this prospering society under the Gods, and grew disgusted at this thought, and decided to bring about its destruction. The Chaos invaded Lenor, and into Equestria. It polluted and corrupted the minds of some of the greatest Alicorn military generals, who turned their subservients over to Chaos. These deformed Alicorns became known as Chaos Alicorns . Headed by the Grandmaster of the Alicorn Military, Eliphas the Greater, and with the help of Discord, The forces of Chaos began their Hundred Years War against the Loyalist Alicorns, led by Sir Pelenal the Vigilant. For 100 years, the forces of Chaos and Order fought. One by one, the great and mighty cities of the Loyalists burned and fell to Chaos. Territories were lost, and great Loyalist generals lost their lives.
After 99 years of bloody war, the only Alicorn city that remained was Canterlot (which was once about 3 times bigger a city than modern times). But, Pelenal's lieutenant, Horus Blackwater, turned to Chaos, slew Sir Pelenal, and sold the city out to Eliphas and his forces. This devastating move made Horus one of the most hated and traitorous figures in the war, especially in Canterlot itself. Eliphas and Horus combined their forces to destroy the last Loyalist city that remained, and crush the empire once and for all. It was in this moment, when all hope seemed lost, that Celestia the Radiant, daughter of Pelenal, took on her father's role as head of the Loyalists. Under her guidance and heroic bravery, the Loyalists buckled down, defended against the forces of Chaos and, in the end, turned the tide of the war by holding the city and breaking the siege.
Celestia challenged Eliphas himself to combat, and, though the battle was hard, Celestia rose victorious, slaying Eliphas. The Chaos Alicorns under his command immediately dissolved. Horus's forces were quickly slain. Horus himself retreated, and his location was never discovered. With the great war over, Celestia was made Princess of Equestria, which was the only territory remaining for the Alicorns. In order to ensure the survival of Equestria, these few remaining Alicorns gave up their powers, and de-volved themselves into the common Equestrian races we know today; Ponies, Pegasi, Unicorns, and Hippocampi. Thus, all Equestrians are descendants of the ancient Alicorns.