The Warden was the cruel administrator of a Fire Nationprison rig in the Earth Kingdom that was specially designed to confine earthbenders. He loved taunting prisoners, whom he saw as savage and barbaric, to eradicate their morale and suppress any thoughts of rebellion. He used brutal punishment to maintain order, and constantly abused the people under his command, even the guards, as he would not hesitate to take extreme measures when he felt that someone disrespected him.
After Katara purposely let herself be captured, she and the other prisoners were brought to the Warden's shipyard, which doubled as a prison, and were personally greeted by the Warden himself. He re-framed the situation as a positive one, telling the prisoners to look at him as their "humble and caring host", with whom they would get along if they did whatever they were told. However, he exposed his true colors when an elderly prisoner coughed during his speech, at which point the Warden firebent at the man's feet and sentenced him to a week of solitary confinement. The Warden gave the other arrivals a tour of the shipyard, emphasizing the fact that the structure was built entirely of metal, and thus they could not escape by bending it. He parted ways with them at the entrance of the prison yard.
Not long after, the Warden witnessed from atop the prison walls Katara's attempt to rile the earthbenders into a rebellion. Though his soldiers moved to stop the waterbender from speaking, he stopped them and allowed her to finish, retreating with a pleased smile on his face as the earthbenders did not have the heart to react.
That night, two patrol guards reported to the Warden that they thought they had seen a flying bison pass over the prison rig. However, the Warden started to lose his patience when one of the guards opted that it looked more like a buffalo. When the guard captain dared to cautiously state that it was irrelevant to know if it was a buffalo or a bison, the Warden angrily threw the man off the rig. Nonetheless, he ordered the remaining soldier to commence a search of the entire facility.
In the morning, Sokka was found to be the intruder. The Warden confronted him and Katara, threatening them to give up as they would otherwise be killed on the spot. In a last attempt to inspire the earthbenders, Aang managed to provide them with the rig's coal supply, but much to the amusement of the Warden, the earthbenders cowered back. He reprimanded Katara for her foolish attempts to change the hearts of the captured benders, pointing out how their spirits had been broken a long time ago.
As he confidently retreated, he was hit on the back of the head by a piece of coal fired at him by Haru. Enraged, he retaliated with two powerful fire streams, but they were blocked by a wall of coal created by Tyro. Realizing that he had a prison riot on his hands, he ordered his soldiers to show no mercy in putting the prisoners down. However, the advantage of the firebenders and guards had disappeared now that there was a bendable substance on the prison yard, and the earthbenders, with help from Team Avatar, soon managed to gain the upper hand. Three earthbenders created a bed of coal underneath the Warden, to levitate him off of the metal island and drop him into the water below, much to the Warden's fear as he proclaimed that he could not swim.
The Warden was a brutal, heartless man whose prisoners and guards suffered due to his cynical methods of operating the facility. He was cruel, merciless, and intolerant of any nonsense or rebellion, punishing one prisoner who merely coughed during his speech, throwing the captain overboard because he did not know the difference between a buffalo and a bison, and threatening to kill Katara when she planned a revolt of the prisoners.