The White Lotus leader is a waterbender and head of the White Lotus which fights to help maintain the balance of the entire world.
The White Lotus leader, along with two other members of the Order, visited the South Pole four years after the death of Avatar Aang in search of his reincarnation to ensure they where able to protect and train them properly. At some point in their search the entered the home of Tonraq and Senna, who happily assured the members that their daughter, Korra, was the person they sought. The White Lotus leader was rather skeptical due to having previously investigated multiple claims in both Water Tribes that all proved false, at this point Korra promptly demonstrated her earthbending, firebending, and waterbending abilities in front of the members of the Order to show off her skills.
The leader was present at Korra's firebending test, and witnessed the young Avatar demonstrate her prowess in the art before the renowned organization and Katara, whom had helped teach Korra waterbending. He however expressed concerns over her lack of restraint in firebending and her lack of interest of the spiritual side of being the Avatar. nevertheless the leader deemed Korra a firebending master and told her that she was ready to commence to her final learn airbending under Tenzin's tutelage.
When Tenzin announced that he could not relocate to the Southern Water Tribe, the White Lotus leader, Tenzin and Korra all discussed the delay of Korra's training and their best course of action to take. When Korra suggested that she could return to Republic City with Tenzin, the White Lotus leader promptly objected, pointing out that it was the Order's task to protect Korra while she mastered the four elements, and that Republic City was too dangerous for her much to her displeasure.
White Lotus leader on the Avatar wiki.