History of Kai (Secrets of the Forbidden Spinjitzu)

Wasted True Potential
Kai is slurping a soda while Cole is playing a game to beat Zane's high score. He is also seen in a red swimming suit and looks a bit plump with all the ninja sitting in the hot tub. He failed against Wu's Chicken and Wu as well with the other ninja in the training session.

A Rocky Start
The Ninja are scrambling around the Monastery trying to get ready to go investigate the Desert of Doom.

Once they’re all packed, P.I.X.A.L. shows them to the Underground Base, where she has made several new vehicles for the Ninja, including the Land Bounty. Zane, Jay, Nya, and Lloyd board the Land Bounty, while Kai and Cole take their own vehicles to the Desert.

When they finally arrive, they set up a camp around an oasis they have found. Zane reads a book about the Desert, telling them that long ago, an ancient tribe once lived in the Desert. They worshipped a thousand year old giant scarab beetle called Beohernie. One day, the beetle went out of control, and destroyed the civilization, seemingly for no reason. The beetle suddenly appears and attacks, and the Ninja make a run for it to the Bounty.

As the beetle chases them, Cole is knocked over, and is almost left behind. He recuperates himself, and the Ninja are continued to be chased by the giant.

While making a run for it, a major component to the Land Bounty is devoured by the Beetle, and the Ninja are left stranded on a plateau, surrounded by two more scarab beetles.

The Belly of the Beast
Zane attempts to repair the Land Bounty, but it will be impossible to escape without the component the beetle ate.

That night, Zane says that the Bounty is useless without the component, and the only way to retrieve it is to go to the belly of the beast itself. He then gets the idea that one of them has to be strapped to a rope and sent into the stomach of the beetle. They play a rock-paper-clamp tournament in order to decide who goes in, and Zane ends up being the winner.

The next morning, they hook up a wire to Cole’s Dirt Bike, and tie it to Zane. Once Zane is inside, he suddenly has another set of visions. He sees an enormous snake made of fire emerge from a pyramid in the Desert, and sees the female snake from his previous dream attacking him in the Underground base. His visions continue, and he sees himself hurt in a world made of ice and snow.

He then awakens in the stomach of the beetle, and finds the component. The Ninja get him out quickly, and they reattach the mechanism to the Bounty, and head off, finally escaping from the three beetles.

Boobytraps and How to Survive Them
Zane and the others meet up with Clutch Powers in his camp in the Desert of Doom. Clutch refuses to enter the temple. The Ninja try to convince him, but he is unwilling. Zane points out that his book, Booby Traps and How to Survive Them, is key in helping explorers enter ancient tombs and whatnot. Clutch suddenly gets a call from the Explorers Club, saying that since he hasn't explored in over 10 years, his membership will be redacted. In order to preserve his place in the Club, he tells him that he will now be exploring the ancient pyramid.

Clutch and the others enter the Pyramid and find that it is filled with booby traps and ancient markings. He tells them that his book is key in surviving. Their first obstacle is a rickety old wooden bridge. Zane and the others stumble across, but they survive without trouble. Clutch tells them they got lucky, but luck runs out.

As they continue through, they trip over a trap that sends them all sliding down a corridor to a pit of spikes. Kai blasts the spikes with his fire, securing their lives. At the bottom of the pit, they find a pathway to the next room.

Finally, they find the main chamber, where several sarcophagi are lined out. In the next room, they find a large puzzle on the wall, and Zane points out that when solved, might lead them to a treasure behind the door.

While Jay attempts to solve it, Zane inspects the ancient markings on the walls. He translates the writing, that is a warning to those attempting to enter the tomb. It tells the story of a serpent who's anger almost destroyed Ninjago, until a foolish boy locked her away. He suddenly has a vision of his dream with Aspheera, and warns the others not to open the door... He is too late, and the sorceress is awakened. Her name is Aspheera. She tells the Ninja to help her find "him," the treacherous deceiver who betrayed her. The Ninja don't know who she is talking about, and attempt Zane and the others attempt to fight her with Spinjitzu, but she too knows the art, and so they are unable to stop her.

She takes an interest in Kai, calling him a fire elemental, and tells him that for thousands of years she has been locked up, cold and alone. She starts to steal his power from him, and the others are no match for her, and she successfully steals his powers, and returns to her true form.

Clutch runs away as the Ninja are tied up in chains by Aspheera. She escapes the pyramid, and unleashes her army of Pyro Vipers onto Ninjago City...