Piandao was born to two firebenders, both of whom were considered prodigies in their art. Ashamed that their only son was not a bender, his parents left him on the doorsteps of an orphanage. Growing up, Piandao was a nervous and agitated child, but he showed interest in the arts and enjoyed painting and calligraphy. It helped him relax and focus his mind.
At the age of ten, Piandao attended a Fire Nation boys' camp where his natural talent with the sword was recognized. He furthered his studies in the army, where he developed a vicious and fearsome sword fighting style. Piandao fought many battles for the Fire Nation and won them all. However, after several years of fighting, Piandao lost his taste for war and sought to become a more enlightened person. He felt increasingly conflicted about the Fire Nation's role in the Hundred Year War, and so he deserted the army and traveled the world for many years, studying under a variety of benders, warriors, and artisans.
After some time, he returned to the Fire Nation and settled in the town of Shu Jing. The Fire Nation Army came to arrest him for deserting the military. In a legendary battle, Piandao defeated all one hundred soldiers. The Fire Nation Army never bothered him again. Some time after this, Piandao trained the young Prince Zuko to wield dual dao swords.
After Sokka concluded that he did not openly contribute to the group, he sought out Piandao. Sokka then traveled to Piandao's castle. During the interview, Sokka humbly admitted his own unworthiness to the master, much to Piandao's surprise. Having grown accustomed to potential students bragging about their own worth, Piandao found Sokka's humility not only refreshing, but exactly what he was looking for. He decided to properly train Sokka. He was set about to do tasks such as landscape painting, rock gardening, and calligraphy, as well as practicing against one of the master's underlings. Piandao believed him to be worthy enough to choose a steel to make his sword. Sokka made a sword out of a meteorite.
When Piandao gave Sokka the sword, Sokka initially refused the blade and confessed the truth about actually being from the Southern Water Tribe. The master attacked him, and they then engaged in a duel. As the duel between Sokka and his master transitioned outside, Sokka used the techniques he had learned —coupled with his youth and agility— to get the upper hand, something the master pointed out several times.
However, the swordsmaster finally gained the upper hand but sheathed his sword before delivering the final blow. He then revealed that he had known Sokka was from the Water Tribe all along just from his name, and also noted that Aang was the Avatar. Nonetheless, he claimed that the art of the sword did not belong to any one nation, and gave Sokka his sword back. When the group left, they were given a bag with a Pai Sho piece, the white lotus tile.
As the doors to the master's home closed, they noticed that the symbol of the white lotus could be seen surrounding that of the Fire Nation.
Several months later, when the group went to find Iroh, they ran into Piandao. They found him near the destroyed Outer Wall of Ba Sing Se, along with Master Pakku, Jeong Jeong, and KingBumi. It turned out that they were all members of the Order of the White Lotus, and were summoned there by a Grand Lotus, Iroh. The masters took the group to their camp, and Piandao showed Iroh's tent to Zuko. Piandao took part in the fight to reclaim Ba Sing Se in the name of the Earth Kingdom, along with the rest of the Order.
Piandao was a master swordsman who incorporated techniques of benders, warriors, and artisans into his swordsmanship; though retired from conflict, he was considered the best swordsman in the Fire Nation's history (and potentially the world's history). His prowess was best renowned from having never lost a single battle and defeating a hundred Fire Nation Soldiers so decisively that he was left in peace afterwards. Despite being middle-aged, he was incredibly swift and agile. When testing Sokka, he was fast enough to move in front of Sokka before the latter realized it. He had an acute sense of hearing and, while temporarily blinded, was able to ascertain Sokka's position by hearing him step on a twig. He was subsequently able to disarm the young swordsman. Piandao is very aware of his surroundings, quickly able to remember their layout and his current location to better handle the situation at hand. He is able to catch a thrown sheath perfectly on his sword even when blinded. In the Battle of Ba Sing Se, he disabled several soldiers with the aid of Pakku. He was arguably the most powerful and skilled non-bender in the world. Considering he was the tutor for Prince Zuko, it is implied that he was highly skilled in dual dao swords in addition to his skills with the Jian.
In additional to his undeniable prowess in wielding a sword, Piandao was equally renowned for his skill in forging and repairing them with high quality and great artistic design. Many of his works became regarded as prized possessions of high price value. His skill could effectively use any form of material to create his swords, even a meteorite. Piandao was also a masterful artist, primarily in calligraphy, which further refined his precision and dexterity for swordsmanship.
A "Pian Dao" (片刀) is a "slashing sabre", a deeply curved Chinese sword, which was very rare. This is probably a reference to Piandao being a swordmaster. Despite his name, Piandao used a "jian" (剑), a straight-bladed short sword.
Like Jeong Jeong and Chey, he also deserted the Fire Nation military and lived. However, unlike the former two who became outspoken against the Fire Nation's cause for imperial dominance, Piandao left the military simply because he grew tired of war in favor of enlightenment.
He was one of a few characters who knew the Avatar was still alive prior to the Day of Black Sun.
Piandao's character design was a reference by the makers of Avatar to Sifu Kisu, the martial arts consultant for the series.