Prior to The Island
At some point, Mammatus became the leader of the Keepers, and was devoted to protecting the Storm Amulet. Prior to the ninja's arrival on the island, Ronin and the Kryptarium inmates created a ship intended to impersonate Wojira, fooling Mammatus and the Keepers into believing Wojira had returned. To appease what they believed was Wojira, they performed sacrifices. At first, they gave the criminals money, but then started to give them fruits and other materials.
The Keepers of the Amulet
Mammatus instructed the Keepers to capture the ninja, doing so successfully. When the ninja arrived to where he was, he believed that the ninja were thieves seeking to steal the Amulet. He explained the history of the Amulet then declared the ninja prisoners.
The Gift of Jay
After Mammatus told the ninja that they will forever be his prisoners, he told the Keepers to take the ninja away. But when Jay introduces himself, Mammatus tells the Keepers to take Jay somewhere else.
Later on, when the Keepers were done placing Jay on one of their boats, Mammatus makes a speech to the Keepers about Wojira and the First Spinjitzu Master, and that they will sacrifice Jay to Wojira so they can keep her submissive.
The Tooth of Wojira
When Mammatus noticed that the ninja were freed from the poles, he and the other Keepers attempt to stop them from rescuing Jay, but failed to do so. After the ninja returned without Jay, he berated them for awakening Wojira. However, he then realized that Wojira was a fake, and explained the full history of how the Keepers gave tribute to a fraud. Wanting to redeem themselves, they gave a map of the coastline.
Later on, Mammatus apologized to the ninja for his acts. He realized the Amulet was missing and was with the other ninja when they caught Clutch Powers stealing it.
- He shares his name with a type of cloud
- Like Wu's chicken, Mammatus has lightning-based powers. However, it is unknown if it's the actual element of Lightning.