Cult to the Avatars

In many locations where past Avatars did good there is still some cult or spiritual reverence to their specific persona, as with the Kioshi Warriors and Kioshi Island.
While mostly a mundane religion, the Cult to the Avatars can sometimes derail into true cult-like structures, with blood-thirsty minions harnessing Spiritual Power for their evil deeds.
These are the four last known Avatars, and the figures the cults still look up to:

Avatar Roku

Roku was a wise and merciful Avatar with good intentions. Living in an period of change, technological revolution, and nationalist expansion, he worked tirelessly to maintain peace between the four nations during a time of complex political issues and tense diplomatic relations. However, he himself acknowledged that he was too indecisive during his lifetime. Roku's long friendship with Fire Lord Sozin resulted in his reluctance to end his friend's life and thus his imperial ambitions. This ultimately led to Roku's death, preventing him from stopping the Great War.

Avatar Kyoshi

Kyoshi had a difficult early life. Abandoned by her parents, she barely survived as a homeless orphan until being rescued by Kelsang who became her de facto adoptive father. She was also not recognized as Avatar until she was sixteen; instead, her friend Yun was declared the Avatar. When the truth about her identity was revealed, Kyoshi's world was thrown into chaos. Yun was sacrificed to a monstrous spirit, and Kelsang was murdered as he attempted to defend her from Jianzhu, Yun's former master and the Earth Kingdom's de facto ruler. Fearful and desperate for revenge against Jianzhu, Kyoshi fled with her other friend, Rangi, and joined her parents' old criminal gang, the Flying Opera Company. With these unlikely allies, Kyoshi consequently traveled the Earth Kingdom and became involved in the criminal underworld while being chased by Jianzhu. After a series of tribulations and personal losses, Kyoshi forged a close bond with her criminal associates, entered into a romantic relationship with Rangi, and helped to eliminate Jianzhu.
In the following years, Kyoshi struggled to find popular acceptance as Avatar and keep the Earth Kingdom stable as Jianzhu's death resulted in tensions and a leadership vacuum. Kyoshi saw the end of the Camellia-Peony War in the Fire Nation, and later dealt with her friend Yun, who had been corrupted by his desire for vengeance against everyone who had lied about his Avatarhood.
These experiences greatly shaped her world view and approach to her role as Avatar. Unlike her successors, Roku and Aang, Kyoshi was determined that only true justice could bring peace and had fewer qualms about killing enemies to achieve this goal if necessary. Employing these methods, she was a generally effective Avatar. She prevented the resurgence of the disastrous Yellow Neck Uprising, stopped Fire Lord Zoryu from massacring the disgraced Saowon clan, defeated an attempted armed takeover of the Earth Kingdom by Chin the Conqueror, founded Kyoshi Island and the Kyoshi Warriors to keep her adopted homeland safe, and helped to reform the Earth Kingdom into a constitutional monarchy. In her later life, she maintained peace between the fifty-five states of the Earth Kingdom and helped implement policies to uplift the poorest and most disadvantaged, and saw the Earth Sages redeemed from a corrupt group of politicians to an order of wise advisors and academics. Living for more than two centuries, Kyoshi led the world into an unprecedented time of peace.
However, some of her actions also caused long-term problems for the Earth Kingdom: The deaths of Jianzhu, as well as Chin and her foundation of the Dai Li, would lead to the decline and eventual fall of her home country in the centuries following her lifetime. After her death, the Dai Li obeyed Earth King Jialun's orders to purge the sages who attempted to maintain Kyoshi's policies of peace and prosperity. Because of this, Kyoshi came to deeply regret the creation of the Dai Li.

Avatar Kuruk

Native to the Northern Water Tribe, he was a powerful and gifted bender who dreamed of changing the mortal world for the better by uniting the people and acting upon the foundations laid by Yangchen. His hopes were dashed, however, after a brutal confrontation with a dark spirit resulted in a deep spiritual corruption that began to fester within him. This clash was only the first of its kind, as an increasing number of dark spirits began to cross into the mortal realm to wreak destruction. To prevent others from being affected with the same sickness that tormented him, Kuruk opted to repeatedly face the wrathful beings on his own. Only his spiritual mentor, Nyahitha, knew about the sacrifices and loneliness he endured.
As he secretly destroyed dark spirits in the mortal and Spirit World, Kuruk began to neglect his regular duties as the Avatar. Physically and psychologically weakened, he spent much of his free time pursuing a hedonistic lifestyle to cope with his stress and spiritual affliction. He eventually ended the worst dark spirit incursion by weakening an especially evil and powerful spirit, Father Glowworm, in a titanic battle. Having incurred the wrath of the spirits for his actions as well as lifestyle, Kuruk was finally punished once more, losing his fiancée, Ummi, to Koh the Face Stealer. He spent his last years trying to save her, but failed. Kuruk eventually died aged just 33, as his spiritual sickness had drained his lifeforce. Since he had done little to solve the mortal world's problems, great upheavals and strife occurred in the four nations upon his death

Avatar Yangchen

After mastering all the elements in her youth, she was eager to make a difference in the world despite her inexperience. She eventually became a respected figure and was hailed for her wisdom, determination, and power. Although Air Nomad culture emphasized pacifism and the sanctity of life, Yangchen was feared for her fierce willingness to do whatever was required to maintain balance and peace throughout the world in her duty as the Avatar.
Due to her devotion, no threats of war occurred for an entire generation after her death. In death, she was revered as a holy individual, and people in the Earth Kingdom even began to pray to her for protection.[9] However, her actions also contributed to a rise in dark spirit attacks during the time of her successor Kuruk