The Avatar: The Last Airbender animated television series and live-action film adaptation, The Last Airbender, features an extensive cast of characters created by Bryan Konietzko and Michael Dante DiMartino. The series deals with a war that was started by the Fire Nation as an attempt to conquer the world, taking advantage of the absence of the Avatar, who alone holds the power to counter Fire Nation aggression. During the Avatar's absence, the balance between the Fire Nation and the three other countries, the Air Nomads, Earth Kingdom, and the Water Tribes, began to deteriorate and plunged the world into a century of war. The first phase of war ended with the elimination of the Air Nomads, near extinction of the Water Tribes, and near-total colonization of the Earth Kingdom, thus setting up the world that the characters of Avatar lived in.
The main protagonist of the series is Aang, the most recent incarnation of the Avatar, who is released from an iceberg after being frozen for a hundred years. With his new friends Katara and Sokka, and later Toph, Aang sets out to master the three unlearned elements and end the war that has ravaged the world during his absence. While primarily focused on Aang, the series also focuses on Zuko, the crown prince of the nation that started a world-domination campaign during the Avatar's absence. Zuko is initially portrayed as an antagonist who tries to capture Aang, but with the help of his uncle, he eventually develops conflicting feelings about the war and later becomes one of the primary protagonists. This change of heart causes the role of the primary antagonist to shift to his sister, Princess Azula, and his father, Fire Lord Ozai.
Character designs were developed through a series of drawings by one of the series' creators, Bryan Konietzko. The main sketch depicted a middle-aged monk with an arrow on his head and later included a flying bison. Konietzko's partner, Michael Dante DiMartino, was at the time interested in documentaries related to the South Pole. They combined these ideas and created the concept of an "air guy" and "water guys" trapped in a snowy wasteland, with "fire guys" invading them. Additionally, the writers based the characters' different bending abilities on distinct styles of martial arts.