"Swordbending" is a comic strip that takes place in Book Three: Fire, originally released by Nickelodeon Comics Club magazine in 2009 and later released by Dark Horse Comics in Avatar: The Last Airbender — The Lost Adventures.
While Zuko performs some stretches before his training session with Aang, Sokka eagerly runs up to him and asks if he is up for some "swordbending", a proposal Zuko refuses due to his duties of guiding the Avatar. Although Sokka presents reasoning for why Aang will not need Zuko's assistance for at least a little while, Zuko offhandedly says that his level of swordbending is too far above Sokka's and offers that battling The Duke would be more fair, then attempts to walk away. This leaves Sokka no choice but to challenge Zuko to a "Swordbending Kai", to which, although wishing to refuse, he says his honor demands that he accept, wishing to make Sokka stop pouting.
A few moments later, Sokka and Zuko are in swordbending-ready position, with Aang mediating between them until the battle begins and Katara, Toph, Haru, Teo, and The Duke seated outside of the ring, wishing to watch the fight. When Aang blows the whistle for the match to begin, Zuko and Sokka charge at each other, Sokka with his space sword and Zuko with his dual dao swords. Katara cheers for Sokka on the Water Tribe front while Toph, who The Duke assists in holding her poster right side-up, hopes for Zuko to win. With some high-level footwork, Zuko manages to gain the upper hand and trips Sokka with his swords, causing Sokka to lose the match. With each successive rematch, the Water Tribesman is unable to defeat his opponent.
Finally, Sokka simply lunges for Zuko with his sword under the pretense of a sneak attack, another tactic that ends up failing when Zuko knocks Sokka's sword from his hands. This is not the last trick up his sleeve, however; he quickly reaches behind his back and grabs the boomerang he had held for the entire battle and throws it at Zuko's head, but the firebender ducks just in time, exclaiming that there should be no boomerangs in swordbending. He stands erect again and tries to correct himself, realizing that he used Sokka's fake word "swordbending", when the boomerang returns and hits him on the back of the head. Sokka explains that although he lost the battle of swords, he won the battle of words.