"The true mind can weather all the lies and illusions without being lost. The true heart can tough the poison of hatred without being harmed. Since beginning-less time, darkness thrives in the void but always yields to purifying light."
— The lion turtle sharing his wisdom with Aang.
The lion turtle was a gigantic, ancient creature with the head of a lion and clawed, lion-like feet. He had existed since the beginning of time and therefore predates the Avatar. This lion turtle was the last of his kind, as the rest were hunted and killed thousands of years ago. Possessing immense power and wisdom, the lion turtle served as a spiritual beacon where Aang could commune with his past lives. When these efforts proved fruitless, the lion turtle revealed to Aang the power to bend the energy within oneself. Aang was not the first Avatar to meet one of these legendary beasts, but he was the first in many ages.
Because of the lion turtle's age, a large forest sprouted on its back. He preferred to stay hidden from the world, with his head submerged so he appeared as an ordinary island.
One night in 100 ASC, a few days before the arrival of Sozin's Comet, the lion turtle appeared off the coast of Ember Island as a small, dome-shaped isle. Aang, who had just come to the abysmal realization that he must kill Fire LordOzai, was subconsciously directed to the island and sleepwalked there with Momo following. By the following morning, the island was gone and with it, Aang and Momo.
While the others were searching for him, Aang woke up the next day to see that the island was now adrift in the middle of the sea. After exploring a little, he found himself at the center of the island where he discovered a hexagonal piece of an unknown material which was part of the lion turtle's shell. He decided to meditate there and to call on his previous incarnations for guidance starting with Roku, then Kyoshi, Kuruk, and finally, Yangchen. After listening to their advice, he realized he had no choice but to kill Ozai.
Eventually, the island approached land, revealing that it was moving; Aang jumped off it and while diving below, discovered it was, in fact, an enormous creature. After approaching the head, he realized it was a lion turtle. Aang asked him for guidance to which the lion turtle replied, "The true mind can weather all the lies and illusions without being lost. The true heart can tough the poison of hatred without being harmed. Since beginning-less time, darkness thrives in the void, but always yields to purifying light." He then imparted an ancient bending art, which had the ability to take away an individual's bending, to Aang before leaving the Avatar and Momo on the Earth Kingdom shore to wait for Phoenix King Ozai, saying, "Wait for him: he will come."
The lion turtle was seen again in a flashback, right before Aang began energybending Ozai, where he spoke the words: "In the era before the Avatar, we bent not the elements but the energy within ourselves..." Aang, with these words in mind, began to bend Ozai's energy. The final time the lion turtle was heard, he spoke the words: "To bend another's energy, your own spirit must be unbendable or you will be corrupted and destroyed..." During this time, Aang's energy managed to overpower Ozai's and he succeeded in taking away his ability to bend.
The chanting that can be heard when the lion turtle called to Aang, causing him to sleepwalk/swim to him is a Buddhist chant, "Na Mo A Mi Tuo Fo Shin Di" (spellings vary). This chanting was heard for the first time when the Fire Sages assumed their stances in front of the door to the Fire Temple sanctuary. It was heard again right before Aang stepped into the Spirit Oasis to fuse with La. Na Mo A Mi Tuo Fo" (南無阿彌陀佛) is from Da Bei Chan Fa (大悲懺法), and translates as "Blessed be Amitabha Buddha."
Nyla was unable to find Aang while he was on the lion turtle due to the fact that the lion turtle had traveled all over the world for so long, accumulating countless new smells, that it smelled like the earth itself, thus masking Aang's scent.
The lion turtle is the oldest and largest living creature in the Avatar World.
The lion turtle was well received by critics of the Sozin's Comet special. However, some critics claim the lion turtle teaching Aang energybending to defeat Ozai without killing him was a deus ex machina, a cop-out used by writers when they have written themselves into a corner, though they claim they had created this concept prior to its introduction. Many were also critical that his voice was too difficult for them to understand.
The lion turtle is one of the few animals that can understand human speech, and it is the only one that can speak human language, however, it does the latter telepathically.
The lion turtle is the only creature and character to be painted, as opposed to being drawn as a cartoon.
This lion turtle bears a striking resemblance with the Island Turtle, a monster from the Yu-Gi-Oh! Trading Card Game.