The Realm of Madness (aka the Dark Realm) is one of the Sixteen Realms parallel to Ninjago. It is described as a place where evil flourishes, because of an imbalance between the forces of light and darkness. The Mountain of Madness is located here, and the native inhabitants include Mud Monsters and Craglings.
At an unknown point in time, the Realm of Madness came into existence as one of the Sixteen Realms.
Contrary to what he led the Skulkin to believe, Lord Garmadon's true goal during his time in the Underworld was to escape his prison, not wield the power of all four Golden Weapons. The reason for this became clear when Samukai claimed all of the Golden Weapons and attempted to use them against Garmadon—the combined power of the weapons was beyond anyone's ability to control.
As Samukai disintegrated into a portal, Garmadon explained to Master Wu and the Ninja that he intended to use the portal to reach a place where the forces of good and evil were unbalanced—there, he could gain the power he needed to wield all four Golden Weapons at once. After a final bitter exchange with his brother, Garmadon fled through the portal, which disappeared once he passed through.
After Lloyd was kidnapped by the Serpentine, Master Wu decided to seek the aid of Lord Garmadon. Traveling to Mistaké's tea shop in Ninjago City, he purchased some Traveler's Tea and used it to transport himself to the Realm of Madness. Upon arrival in the dark realm, Master Wu was immediately confronted by Lord Garmadon himself, who had been mutated during his time in the dimension.
Now sporting new armor and an extra set of arms, Garmadon attacked his brother, forcing him into a mud pit with three Mud Monsters. Before the creatures could envelop him, Master Wu revealed Lloyd's plight, prompting Garmadon to save his brother and agree to a temporary alliance in order to save his son.
With that settled, the brothers set out for the Mountain of Madness, where Garmadon said they could find a portal that would return them to Ninjago. As they walked, Master Wu brought Garmadon up to speed on what was happening in Ninjago, prompting the four-armed villain to express regret that Lloyd had tried to follow in his evil footsteps.
After climbing the Mountain of Madness and fending off a Cragling attack, Wu and Garmadon finally reached the portal that would allow them to escape the dimension. At that moment, Garmadon pushed Wu into the portal, gloating that he had only agreed to the alliance so he could return to Ninjago and steal the Golden Weapons—thanks to his time in the Realm of Madness, he could now wield all four at once. With that, Garmadon jumped into the portal himself, reappearing in Ninjago with his brother.
After several adventures with the Ninja and his brother, Lord Garmadon went to Mistaké's shop to order some Traveler's Tea, apparently intent on returning to his dimension. Before Mistaké could fill the order, however, Garmadon had left the shop to aid the Ninja against the Great Devourer.
During Fenwick's explanation of the sixteen realms, one of the realms he showed the Ninja was the Realm of Madness.
- The Realm of Madness has three known methods of entry and exit: the portal opened by attempting to wield all four of the Golden Weapons, Traveler's Tea, and the Realm Crystal.