"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 is a gigantic, ancient creature who has existed since the beginning of time, and is one of the few known animals to have lived in the era of Raava. This lion turtle is the last of his kind, as the rest of the lion turtles were hunted and killed thousands of years before the Hundred Year War.
Aang communed with his past lives in hopes of finding a way to end the Hundred Year War while on the lion turtle. After the previous Avatars failed to provide Aang with a satisfying solution, the lion turtle revealed to him the power to bend the energy within oneself, which the Avatar later used to remove Fire LordOzai's bending abilities.
Having lived for eons, a large forest had sprouted on the lion turtle's back. He prefers to stay hidden from the rest of the world, and submerges his head underwater in order to appear like an ordinary island.
One night in 100 AG, 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 Lord Ozai, was subconsciously directed to the island and sleepwalked there, with Momo following closely. The creature, along with Aang and Momo, were gone by the following morning.
Unaware of the time and the frenetic searching for him by his friends, Aang awoke the next day to find 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 unknown material which, unbeknownst to him, was part of the lion turtle's shell. Eventually, Aang decided to meditate there and call upon his previous incarnations for guidance, starting with Roku, followed by Kyoshi, Kuruk, and ending with Yangchen. After listening to their advice, he realized to his dismay that 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 that it was actually 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 subsequently imparted the knowledge of an ancient bending art to Aang before leaving the Avatar and Momo on the Earth Kingdom shore by Wulong Forest to await the arrival of Phoenix King Ozai.
As Aang was about to remove Ozai's bending, the lion turtle appeared before the Avatar in a flashback, stating, "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 warned that in order to bend the energy within another individual, the practitioner's "own spirit must be unbendable" or they "will be corrupted and destroyed". During this time, Aang's energy managed to overpower Ozai's and he succeeded in taking away the Fire Lord's ability to bend.
In early production, a very high level of detail went into the lion turtle's design. In the final animation, however, the lion turtle was not rendered quite as intricately.
The lion turtle resembles Chinese mythological turtles, a few of which are placed around the Forbidden Palace in Beijing.
The chanting that can be heard when the lion turtle called to Aang, causing him to sleepwalk and swim toward 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 it had traveled all over the world for so long, thus accumulating countless smells in the process. In essence, the lion turtle smelled like the earth itself, effectively masking Aang's scent.
The lion turtle was well received by some critics of the Sozin's Comet special. Others, however, claim that 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 to understand.
The lion turtle is the only creature and character to be painted, as opposed to being drawn as a cartoon.