Centuries ago, a single drop of moonlight fell from the heavens and transformed into an opal, carrying the power to destroy and kill all who tried to claim its power. To prevent this from happening, a kingdom was created around the opal, and the rulers took an oath to keep the Moonstone's power from destroying the rest of the world. The responsibility of protecting the Moonstone was passed down generation after generation among the Kings and statues were built for each of the past rulers for fulfilling this duty.
Centuries later, the kingdom was ruled by King Edmund and his wife who gave birth to a baby boy. However, the Black Rocks, the creations of the Moonstone, began to ravage the Dark Kingdom, transforming it into a wasteland as they continued to grow and spread all throughout and even within the castle. King Edmund couldn't bear the situation anymore and tried to destroy the opal. However, his attempts failed and caused a catastrophic event that nearly destroyed the Dark Kingdom. King Edmund survived the calamity, but his attempts to destroy the stone cost him the loss of his right arm and the death of his wife. In the aftermath of the tragic events, King Edmund realized with the Moonstone still existing, the Dark Kingdom was no longer safe and ordered his subjects to evacuate and never return for their own safety. King Edmund also made the difficult decision to send his son away with a servant woman to protect him. The King then advised his most trusted and skilled warriors, known as the Brotherhood to leave the castle and keep anyone from finding the Moonstone. Since then, King Edmund would remain behind to keep his oath of protecting the world from it as well.
Twenty-five years later, King Edmund meets Rapunzel and her friends who come to the Dark Kingdom to fulfill Rapunzel's destiny to grab the Moonstone to restore balance to the world. The king is determined to stop them, but upon doing so discovers his son Eugene among Rapunzel's company. King Edmund is delighted and believes the return of his son is a sign that together they would finally destroy the Moonstone, freeing their family from their destiny of protecting the powerful opal. Although reluctant, Eugene decided to aid his father to destroy the Moonstone for good in fear of losing Rapunzel after learning his mother's death was also caused by the opal. However, Eugene found himself greatly conflicted and unsure after coming to learn the truth about his past and family, leaving him wondering who he really was. Rapunzel and the group managed to enter the castle through the underground sewers and once again found themselves battling against King Edmund, guarding the Moonstone's chambers.
Rapunzel and the group fought against the king, but were swiftly defeated. Rapunzel and King Edmund confronted each other until they were interrupted by the arrival of Eugene, who after a change of heart, stood by Rapunzel with his relationship toward King Edmund revealed in the process. However, as Rapunzel was about the enter the Moonstone chamber, the statues of the previous Dark Kings arose to uphold their oath that no one gains possession of the Moonstone. Rapunzel and her friends fought, but realized that no matter the number of times they defeated the ghosts, they continued to rise again. Through the quick thinking of Lance, however, they defeated the ghosts once and for all by destroying their statues and received help from King Edmund after Eugene successfully managed to change his mind.
With the threat over, Rapunzel, Eugene and Cassandra entered the Moonstone chamber at last. Rapunzel's presence reacted once again with the Moonstone, causing all the Black Rocks inside the chamber to completely smooth all over as a path was created for Rapunzel. After saying her final words to Cassandra and Eugene, Rapunzel approached the Moonstone, but before she could fulfil her destiny, Cassandra snatched it away from her and claimed she was fulfilling her own destiny. The Moonstone began to surge with power, causing Rapunzel and Eugene to be blown back to the entrance and watched in horror as they witnessed Cassandra merge with the opal and the fulfilment of Lord Demanitus prophecy.
In the aftermath of Cassandra's transformation, she revealed to Rapunzel and Eugene that during their previous adventure in the House of Yesterday's Tomorrow, she discovered the truth that she is actually the biological daughter of Mother Gothel, who abandoned her after kidnapping Rapunzel during her infancy. With the discovery of her past and believing she will always be cast aside in favour of Rapunzel, it was the last straw which ultimately lead to Cassandra's betrayal. Despite everyone's efforts to stop or reason with her, Cassandra quickly made her escape and stole Adira's Shadow Blade in the process. Rapunzel followed Cassandra, attempting one last effort to reason with her before she went too far, but she refused to listen and officially cuts ties with Rapunzel and their friends as she fled the Dark Kingdom.
Following Cassandra's betrayal, Rapunzel and the group left the Dark Kingdom shortly after Ulf arrived and warned them that Corona is currently in danger. Adira and King Edmund remained behind and watched as the group left. King Edmund later left the Dark Kingdom to visit his son in Corona to give him a family heirloom while also hoping to reconcile and build a relationship with him. Cassandra is later revealed to still remain on the outskirts of the kingdom as she learns to control her newfound powers with the aid from a mysterious enchanted girl. Eventually, Cassandra and the Enchanted Girl left to seek out information to help them to destroy Rapunzel, leaving the Dark Kingdom completely and fully abandoned.
In the series finale, "Plus Est En Vous", following the defeat of Zhan Tiri, King Edmund, Adira and Hector decided to return to the Dark Kingdom to rebuild and restore the kingdom to it's former glory and discover the Black Rocks that originally overridden the Dark Kingdom completely have all disappeared, allowing life to blossom and return once again.
Places of interest
- The Throne Room: Located outside the Vault, it features the emblem of the Dark Kingdom engraved on the floor and statues of all the previous Dark Kings.
- The Vault: Located deep underground, the vault is a special place within the castle that contains the Moonstone, featuring a long bridge from the entrance leading to the cage containing the opal.
- The Dining Room: Located inside the castle, it includes a long dining room table with nine chairs and a fireplace with a portrait of King Edmund and his wife hanging above.
- The Cable Car Station: It is the only pathway to access to the kingdom from outside, over the valley of black rocks.
- The Sewer: The alternative path to the Moonstone vault that is covered with lava.
- The comet shaped emblem of the Dark Kingdom is also featured as the mark on the hands of Quirin and Adira.
- The ancient scroll illustrates the Kingdom's castle along with the Sundrop Flower.
- The kingdom is protected by a group of warriors known as the "Brotherhood". King Edmund, Quirin, Adira and Hector are members and each of them have the Dark Kingdom's symbol on the back of their left hands.