The legend of Lord Demanitus was first mentioned by Xavier in "Queen for a Day". Demanitus was in a constant battle against the demon Zhan Tiri and her servants. Years later, Zhan Tiri cast a spell to cause the blizzard and storm sweeping across the land of Corona. Demanitus used both magic and science to build a machine deep in the Corona mountains and change the direction of the wind. He successfully defeated Zhan Tiri and saved the day. Over the years, Demanitus captured many of the evil spirits and imprisoned them in the chamber of the machine.
Demanitus and three of his pupils researched the legend of the Sundrop and Moonstone, two elements created and were divided by a mysterious cosmic event that are longed destined to be reunited. Alas, they were unable to find them. Unfortunately, they weren't the only ones searching. Demanitus' pupils suddenly betrayed him and summoned his old nemesis, Zhan Tiri, whom Demanitus eventually banished back to her own realm. Demanitus knew his research of the Sundrop and Moonstone was too valuable, so he decided to tear the scroll containing his research into four pieces, which were scattered across the world, preventing them from falling into the wrong hands. The final piece was placed in a maze to keep out those who are unworthy.
To avoid Zhan Tiri's searching, Demanitus used his scientific acumen coupled with an ancient spell to to get an appearance of a monkey by the name of Vigor. However, his conscious was only able to dominate Vigor once for a few hours, which Demanitus saved for his destined encounter with Rapunzel.
Role in the series
Demanitus was first mentioned in "Queen for a Day", when Xavier told the story of the Demanitus Device to Rapunzel and her friends. When Zhan Tiri's snow storm hits Corona, Rapunzel uses the Demanitus Device to save her kingdom.
Lord Dermanitus is mentioned in "Rapunzel and the Great Tree". As told by Adira, when Zhan Tiri took over and corrupted the Great Tree, he put a stop to her reign with a magic spear that rendered the evil magic in the Great Tree dormant. Since Hector discovered the Heart of Zhan Tiri's Tree, he says to Lord Dermanitus to forgive himself "for unleashing the evil that sleeps within".
Lord Demanitus appears again in "Lost and Found", inhabiting the body of Vigor. As Vigor led Rapunzel and Eugene to the Path of a Demanitus, Eugene complained that Demanitus should've made them a map. It was then that Demanitus revealed himself and explained the history of the Sundrop and the Moonstone as well as his own history with Zhan Tiri. He informed the couple that hid the fourth and final piece of the Graphtic Scroll in the maze and assisted them in navigating through its various riddles and traps. However, Demanitus' insistence on navigating through faith conflicted with Eugene's stubborn attitude. When they reach the center of the maze with the scroll piece locked in a chest above a lake of acid. Demanitus encouraged Eugene to take a walk of faith across the fragile crystal bridge and tossed him the "mon-key" required to open the chest, only for Eugene to fail to react in time, resulting in the key falling into the acid; Rapunzel told Eugene to simply pick the lock.
Just after they reassemble the scroll, they are suddenly attacked by a stone guardian, which was activated by Eugene selfishly refusing to drop a coin in a fountain at the start of the maze. Managing to find refuge, Demanitus realized his time was almost up and told the couple that his scroll contains instructions on how to combine the Sundrop and Moonstone and wield the ultimate power, hence the tests of faith. When Eugene suggests they leave the Moonstone alone, Demanitus argued against it, warning that if left alone, the Black Rocks would eventually reawaken and continue to pursue Rapunzel, destroying everything in their path. He counseled Eugene to find the faith he has in Rapunzel if they hope to escape. With his time almost up, Rapunzel begged him not to leave when she had so many unanswered questions about her hair and the Moonstone. He told her to find the answers to those questions on her own and expressed his gratitude at finally meeting the Sundrop. Shortly afterwards, Demanitus' mind would retreat into Vigor's body forever.
After Rapunzel's hair destroyed the guardian as well as create a path out of the maze, they part ways with Vigor, but not before he passes Eugene his turban's jewel. Eugene later finds a final prophecy from Demanitus, warning that at the end of Rapunzel's journey, a member of her party will betray her.
Demanitus was mentioned again in "Be Very Afraid", by Rapunzel when she told Varian the time she met Demanitus in "Lost and Found" when he controlled Vigor at the Path of Demanitus. He was later mentioned again by Varian in "Cassandra's Revenge", once he learned how Demanitus had hidden the fourth incantation within the Demanitus Scroll and called the Lord a genius. Demanitus is mentionned once again in "A Tale of Two Sisters" by none other than his archenemy, Zhan Tiri, who is the one who manipulated Cassandra into betraying Rapunzel and taking the Moonstone for herself and had finally managed to escape her prison thanks to a clash between the Rapunzel's Sundrop powers and Cassandra's Moonstone powers she orchestrated. Arriving in the Demanitus Chamber, Zhan Tiri tells Demanitus he's lost since she escaped her prison and gloats that an incoming eclipse will allow her to steal the both Sundrop and the Moonstone's great powers from Rapunzel and Cassandra and absorb them into herself.
In "Plus Est En Vous", it was revealed that Demanitus tried to talk Zhan Tiri out of her quest for power, but she wouldn't listen and she accused him of turning his back on her. So, as a last resort, he reluctantly used a portal he built to send her to the lost realm. Then he dismantled the device before emerging himself to Vigor, who was his pet, with a device he made. Over two thousand years later, his portal will be assembled again by Varian and the people of Corona in attempt to defeat Zhan Tiri, only for it to be destroyed in the chaos. Regardless, Zhan Tiri is defeated for good when Rapunzel and Cassandra make amends and combine the Sundrop and Moonstone, fulfilling Demanitus' legacy.