Why did Princess Celestia banish Luna?

Nightmare Moon is a dark and formidable alter-ego of Luna, a character deeply rooted in the mythology of the series. This sinister form emerged a millennium before the events depicted in the show, transforming Luna into a being of pure evil and chaos.

The transformation into Nightmare Moon was so profound and terrifying that it prompted Celestia, Luna's sister and ruler of the day, to take drastic action. Recognizing the threat that Nightmare Moon posed to the land and its inhabitants, Celestia banished her to the moon, sealing her away for an entire century.

As the years passed, Luna remained trapped in her Nightmare Moon form, trapped in an eternal cycle of darkness and solitude. Her imprisonment was a punishment for the atrocities she had committed while under the influence of her alter-ego, a reminder of the devastating consequences of unchecked power and ambition.

However, even the most severe of punishments could not keep Luna trapped forever. After a thousand years of confinement, Luna finally returned to Equestria, determined to reclaim her rightful place as ruler of the night. But her return was not met with open arms, as the Mane Six, a group of powerful and heroic ponies, stood ready to defend the land against her.

The confrontation between Luna and the Mane Six was intense and dramatic, with both sides fighting with all their might. But in the end, Luna's time as Nightmare Moon had taken too much from her, and she was ultimately defeated by the brave and resourceful Mane Six.