The Battle at the Wulong Forest was the final battle of the millenium long War, and coincided with the Liberation of Konohagakure and The Shadow Revolution. An airship armada of the Order of the Apocalypse led by self-proclaimed Phoenix King Kenji Hyuga attempted to use the Shadow-enhancing power of the Pole Star to destroy the Earth. The operation was opposed by select members of the Yonkou.
As a result of this battle, Kenji was stripped of his power (leaving him with nothing but his chakra to keep him alive), and Vessel Seireitou became fully realized and regained his ability to use the Ragnarok State. The entire armada of Airships were destroyed. Surrounding areas were severely damaged.
Now stripped of his ship, Kenji begins to attack the Vessel with furiously powerful shadow blasts, but Seireitou pleads for him to stop the war. Kenji merely mocks his efforts and resumes his attacks, which Seireitou barely manages to avoid. All of Seireitou's bending proves useless against Kenji's enhanced dark energy attacks, and growing tired of Seireitou evading all his attacks, Kenji unleashes a powerfully enhanced strike of black lightning at the Vessel. Seireitou manages to catch the black lightning, to Kenji's surprise, and Seireitou prepares to send it right back at him. However, still not wanting to kill Kenji, his only brother, he instead redirects it into the sky. Kenji takes advantage of Seireitou's mercy and successfully hits him with a blast of energy.
Seireitou manages to recover from the attack and earthbends a stone sphere around himself to buy time to think about how to defeat the Phoenix King without taking his life. Kenji's energy overwhelms his stone sphere, and Seireitou nearly loses consciousness from the energy. He is knocked into a mountain and he enters the Ragnarok state through shock, this time all its power is under his control. While in the Ragnarok state, he easily shrugs off Kenji's attacks and traps him with earthbending. The collective Vessel spirits prepare to kill Kenji, but Seireitou resists and gains control again. Kenji taunts him for his weakness and tries to attack Seireitou again, but he's quickly disabled and imprisoned with earthbending. Seireitou finally understands what Irounaku meant, and uses a new type of bending, spirit-bending, to strip Kenji of his power for good.
The battle ends in Seireitou's victory and Kenji arrested and locked in Inperushima.