|“Actually, it's Kapau and Chope—”|
|— Kapau to Chen|
Kapau was one of Master Chen's Anacondrai Cultists. Unlike most members of Chen's army, Kapau and his best friend Chope tended to get in a little mayhem with their tasks, though they dreamt of rising up the ranks of Chen's cult. In the midst of the Tournament of Elements, their loyalty to Chen grew, as they eventually captured Kai and Skylor and allowed for the transformation spell to be completed.
With Chen's army transformed in Anacondrai, Kapau and Chope set off to Kryptarium Prison to capture Pythor, the last of the Anacondrai, whose sweat could be used to make the transformation permanent. Kapau and Chope fought the Ninja at the prison, eventually being aided by their fellow cultists, who captured Pythor.
Kapau joined the cultists as they set off to the Corridor of Elders to battle the Elemental Masters, as he helped carry a Roto Jet with Chen inside. Kapau fought against the Elemental Masters and their allies, with Chen's army slowly overwhelming them. Garmadon made the fateful decision to be banished to the Cursed Realm, which in turn released the spirits of the Anacondrai generals. The generals cursed Chen's army, including Kapau, and sent them to the Cursed Realm.
Some time later, Nya unlocked her True Potential to destroy The Preeminent, the physical manifestation of the Cursed Realm. Consequently, the Cursed Realm was destroyed along with all its inhabitants, including Kapau.
On the first night of the Tournament of Elements, Kapau and several other Cultists made their way to the Anacondrai Temple to partake in a secret ceremony, but were captured by the Ninja who went in their place.
On the day of a feast in honor of the final eight competitors, Chope and Kapau stood guard at the Kabuki's entrance to the palace.
Later, while guarding the bridge to the waterfall, Chope and Kapau heard a guitar solo emanating from the waterfall and began dancing to it until they were ordered to investigate by Eyezor. They found the D.B. Express hidden inside with Dareth jamming out. When Dareth attempted to escape in the DB X, Chope and the other guards pursued him, and managed to capture the brown ninja.
While on duty, he and Chope discussed what their names should be. Later, they brought Lloyd to the ceremony.
While hiding behind the waterfall, Kapau and Chope were ecstatic at being in Chen's inner circle and guarding Skylor, though she messed with them to get Eyezor to yell at them. They released her under Chen's orders and were sent to recapture her, which they successfully did, catching her and Kai in a vengestone net.
The two then performed the spell in Clouse's place due to his being sent to the Cursed Realm, and they both were amazed with their new forms and left the island with Chen and the other Cultists.
Kapau and Chope tells Chen the spell is wearing off because the essence of a true Anacondrai is needed to make it permanent.
Later, Kapau helped infiltrate Kryptarium Prison and fought the Ninja. After getting Pythor, they went back to their hideout.
Kapau and the rest of the army fought the Masters and citizens of Ninjago at the Corridor of Elders.
They nearly got past their enemies before they were shocked to see the spirits of the Anacondrai Generals who were freed after Garmadon sacrificed himself. Kapau along with his allies was banished to the Cursed Realm by the spirits.
Sometime after his imprisonment in the Cursed Realm, Kapau eventually transformed from his Anacondrai form back to his normal self, due to the fact that the spell to turn the Cultists into Anacondrai was never permanent.
While he is not seen nor mentioned in the episode, Kapau was imprisoned in the Cursed Realm, which is revealed to be the stomach of The Preeminent. When Morro and his army of ghosts free The Preeminent, they attack Stiix and its civilians. Eventually, the Preeminent heads out into the Endless Sea but is knocked over by a massive tidal wave created by Nya, killing the beast. As a result, the Cursed Realm is destroyed and all its inhabitants are killed, including Kapau.
Kapau wears a large Anacondrai skull atop his head. He has red markings on his eyes and purple Anacondrai markings on the left side of his face and his forehead. He sports a large, leather, dark red pad on his right chest, which itself is connected to a dark red strap holding two grey knives. Below this, a printing of an Anacondrai Snake is seen on his chest. He wears a dark red and black belt with golden studs and Anacondrai skull-prints on it. His upper legs are dark red with golden chains, while his lower legs are purple with silver chains and claw-prints on his feet.
Kapau and his friend Chope don't have a lot of skill or talent, but they have plenty of ambition despite their comical shortcomings. As the secret plan to transform the Cultists into Anacondrai progresses, they find themselves gaining the higher rank they have always wanted, but they also find themselves in way over their heads. With help from Chope, they complete the spell to turn the Cultists into Anacondrai, and the new Serpentine War begins.