|“There is only one way to return to Ninjago. But to get there, we must pass through the Mountain of Madness and it is a long and dangerous road ahead.”|
|— Garmadon to Wu in "Once Bitten, Twice Shy"|
Lord Garmadon immediately attacked his brother, revealing that his time spent in the dark realm has given him four arms and the power to safely wield all four Golden Weapons. Lord Garmadon nearly defeated Master Wu by summoning Mud Monsters to smother him, but Master Wu managed to deliver the news of Lloyd's plight moments before he was swallowed by the mud. Upon learning that his son was in trouble, Lord Garmadon saved Master Wu and offered his assistance.
Since Master Wu had used all of his Traveler's Tea to reach Lord Garmadon's dimension, the brothers set off for the Mountain of Madness, where they could find a portal that would take them back to Ninjago. Along the way, they had to fend off a Cragling attack with their Spinjitzu. When they reached the portal, Lord Garmadon claimed that he had only been using Master Wu to return to Ninjago, but the brothers nonetheless used it to return to their native realm before regrouping with the Ninja at Destiny's Bounty.
- Its name is similar to the main location in the 1931 horror/sci-fi novella, "At the Mountains of Madness."