Body markings, widely used in the World of Avatar, are applied for a variety of traditional uses. While sometimes used for fashion, they mainly serve as a symbolic mark of identity and responsibility in battle or as a cultural icon.
Airbending master tattoos
Upon reaching master status, airbenders are tattooed with five light blue arrows: one extending from the base of the spine to the forehead, one for each arm pointing to the hands, and likewise for the legs and feet. This pattern is an emulation of the flying bison's natural markings, as they were the first airbenders. Unlike most master airbenders who gain their status later in life, Avatar Aang received his tattoos when he was only twelve, following his invention of the air scooter. This made him the youngest known airbending master until his granddaughter Jinora received her tattoos at the age of eleven in 171 AG.
The earliest known ancestors of airbenders lived on top of the air lion turtle and had similar tattoos along their bodies, though the ends were similar to an upside down "T" with a dot beneath it, and they received them even as children. As they only received the power to control air while out of the city, the tattoo was not yet associated with airbending mastery.
As they run along chi paths, the Air Nomad tattoos of an Avatar will glow when they enter the Avatar State. If the Avatar's body has received a severe injury on a tattooed area, leaving a scar deeper than the tattoo, then that particular spot will not glow.
Mark of the Brave
The Mark of the Brave is a crescent-shaped mark that resembles the moon and is given for "inspirational displays of courage." During Sokka's rite of passage, Katara held the position of bravery as she needed to secure the boat's mainsail and thus prevail against the brutal winds. Following her successful completion of the ritual, Bato bestowed the Mark of the Brave upon her.
Mark of the Trusted
The Mark of the Trusted is a horizontal arc given to outsiders who are able to prove themselves worthy of the Water Tribe's trust. For example, while ice dodging, Aang controlled the jib of his group's cutter to successfully navigate the rocky waters; this position related to trust, as without a steady hand, the whole crew would go down.
Mark of the Wise
The Mark of the Wise is a horizontal arc above a dot and is given for deft decision-making and the ability to maintain leadership under pressure. Hakoda received this mark, and years later, so did his son, Sokka, for steering the boat as well as for leading Aang and Katara wisely through the rough waters by instructing them on what to do.
Water Tribe Warriors, elite nonbending fighters of both the Northern and Southern Water Tribes, bear traditional full-face war paint when going into battle, colored primary black, gray, and white. In the Northern Water Tribe, it is also customary for the chief to ceremonially apply three red markings to the forehead of chosen warriors departing on a dangerous mission.
Earth Rumble VI
Different brawlers in Earth Rumble VI would sometimes possess different tattoos, body paint, or make-up. For example, The Boulder possessed a tattoo a badgermole on his back, a self-proclamation of his earthbending prowess, and Headhunter's face was painted as part of his fighting persona.
The warriors of Kyoshi Island have a strict garb they wear for battle and training. This uniform, which included facial paint, was designed to resemble the attire that Avatar Kyoshi wore during her life, and the face paint itself was meant strike fear into the hearts of their opponents.
Combustionbenders, firebenders with the rare ability to shoot an explosive beam from their forehead, have the tattoo of a third eye on the spot where their attack is released. Although this tattoo marks the point of power, it also marks their weakness, as if so much as a pebble were to touch the spot, the bender's chi would be temporarily blocked, stunning their attacking powers. Although similar in the fact that it is the tattoo of a vertically placed red eye, the details surrounding the eye can vary.
Members of the Sun Warriors bore two red markings on their cheeks, foreheads, noses, and various other spots on their faces and continued to keep them on throughout several different occasions. All members of the tribe wore paint in this fashion, excluding the Sun Warrior chief. The tribal chief instead bore red war paint from below the eye area, up into his face; this face paint was bordered by a level of white face paint.
The Yuyan Archers bear dark red tattoos that run as a strip across their eyes and narrow over the bridge of their nose. The placement of their tattoos symbolizes the importance of sight in their deadly skill. Similar to those of master airbenders, the tattoos of the Yuyan Archers identify them as part of an elite group.
Official Avatar Aang Fan Club
In the Yu Dao chapter of the Official Avatar Aang Fan Club, the girls took mastering a kind of faux airbending very seriously and even began tattooing themselves in a way similar to master airbenders. However, Avatar Aang saw the tattoos as a disgrace to his culture, so as he began to teach the club members about his culture and renamed the fan club the "Air Acolytes", the practice of tattooing was disallowed.
Other groups and individuals throughout the four nations also bear tattoos, which do not generally seem to have any significant meaning. The bounty hunter June, for instance, had a red tattoo depicting a coiled snake on her shoulders.
In the group of pirates that attacked Aang and later Zuko, several seemed to possess tattoos. Although there did not appear to be a significant meaning to the tattoos, they still seemed to be fairly common.
Many prisoners in multiple nations seemed to bear various tattoos. Like the pirates, the prisoners' tattoos did not appear to have a particular meaning behind them, though they were certainly a common practice among criminals as a prisoner from Chin Village told Aang that his tattoos would help him "fit in real well". Two known examples are the scary prisoner himself, who possessed a large green serpent tattoo that swirled around his body, and another from the Boiling Rock who had an elaborate black tattoo.