Fall of the Moon Kingdom (SMCU)

The Fall of the Moon Kingdom was a battle that took place 1,000 years ago at the Moon Kingdom.

Prelude: An Unholy Pact
Queen Nehellenia, Queen of the Dead Moon, attends the celebration of Princess Serenity II's birth 1,200 years ago, at which point she confronted Queen Serenity I, who used the Moon Wand to seal Nehellenia inside a dark mirror forever. In retaliation, Nehellenia cast a curse that the Moon Kingdom would fall and the princess would never inherit the throne. Due to being sealed inside her mirror world, Nehellenia was able to live on even after the destruction of the kingdom.

Beryl, an Earth sorceress of a lower rank, fell in love with Prince Endymion but her love went unrequited. She became obsessively jealous upon finding out his love for Princess Serenity II.

Around 200 years after Nehellenia’s imprisonment, Beryl came across Nehellenia’s dream mirror, where the Queen of the Dead Moon offers Beryl assistance in her obsession to overthrow the Moon Kingdom. Nehellenia then asks Beryl to seek Queen Metallia, the Queen of the Dark Kingdom, who resides in the far side of the Moon.

The rise of Queen Beryl
Main article: Queen Metallia’s Dark Kingdom meeting

In response to Beryl’s confessions, Queen Metallia, the Queen of the Dark Kingdom, called a meeting for her followers in the far side of the Moon. There, she gave a rousing speech, in which she shared her idealist perspective of the Moon Kingdom, as well as her vision of the future, which holds a great and terrible war that would soon spell doom to the Moon Kingdom, along with a victory for the Dark Kingdom. Openly noticing a team of Sailor Senshi sent by Prince Endymion and Princess Serenity II, who had secretly infiltrated the rally, Metallia invited them into a circle of dark energy she made.

Metallia then tests the loyalty of her followers: those who entered the dark energy circle with complete fidelity and believed in her cause would survive; those who did not, would be engulfed and perish. All four Knights of Endymion (Jadeite, Nephrite, Zoisite and Kunzite) and Beryl joined Metallia into the circle, despite objections from Endymion and Serenity II. Metallia christened the newly-converted Beryl, bestowing her the title of Queen of the Dark Kingdom before entering her body. Queen Beryl proceeded to mock Princess Serenity before unleashing a powerful blast of dark energy.

Queen Beryl later retreats to the Dark Kingdom’s headquarters at the far side of the Moon, where she demonstrates her newfound power.

The battle
Queen Beryl raised up the citizens of Earth in a war against the Moon Kingdom. As a result, the Moon Kingdom was completely destroyed, with Prince Endymion, Princess Serenity and her guardians all dying in the battle. When the prince tried to persuade his people not to fight against the people of the moon, Beryl killed him with a sword.

The war was the end of the First Silver Millennium. The Outer Senshi, who were not present at the fight, were drawn to the destruction of the Moon Kingdom, where their talismans unleashed a hidden power, including Sailor Saturn, who used the Silence Glaive in an attempt to contain Metallia's growing dark power, destroying the remains of the Moon Kingdom, and all who survived, including herself, in the process. Everyone was reborn into the present day as a result. Despite the destruction, the Moon Palace remained standing in the Sea of Serenity.

Confrontation of Queens: The Final Battle
Main article: Duel between Queen Serenity I and Queen Beryl

At some time during the battle, Queen Serenity I decided to confront her powerful new rival. The confrontation and subsequent duel became one of the most famous battles during the fall of the Moon Kingdom, which eventually saw Queen Serenity, with the help of her daughter Princess Serenity II, winning the duel using the Holy Blade. A slash from the blade wielded by Princess Serenity cut through Beryl's body, releasing Queen Metallia in her ethereal form in the process.

Despite the victory by the Moon Kingdom royals, it was too late to win the war when Princess Serenity dies of a broken heart after Endymion's death. In response, The Queen then used the Silver Crystal to seal away the Dark Kingdom's powers including Queen Metallia and sent her daughter, Prince Endymion, and the fallen Guardian Senshi to be reborn on Earth during the 21st century. This all came at the cost of her own life though.

Aftermath
After the events in the Moon Kingdom everyone was reborn on Earth, Beryl included. The prince and princess were reincarnated as Usagi Tsukino and Mamoru Chiba and even before they recovered their memories, they succeed in finding each other once again. Meanwhile, Beryl, a normal woman then, found the ruins of the Dark Kingdom at the far side of the Moon during a lunar mission and reawakened Metallia, thus making Beryl remember her past and make her evil again.

The reincarnated Sailor Senshi become close friends with Usagi; through their efforts, the reinstated Dark Kingdom and even Metallia herself are destroyed.

The Moon Kingdom and its castle are eventually resurrected in 2015, where it became the current Solar System Sailor Senshi’s lunar base of operations. However, Usagi and the Sailor Senshi continue to live on Earth with Mamoru while protecting the universe from new enemies in the future.