Moon

The is a planetary body orbiting Earth. It was created a millennium ago by Hamura and Hagoromo Ōtsutsuki, the former of which gave it its name.

History
The Moon was created by Hagoromo and his brother, Hamura, when they sealed their mother, Kaguya Ōtsutsuki, with Six Paths — Chibaku Tensei. After the Moon's creation, Hamura took leadership of the Ōtsutsuki clan and settled on the Moon in order to guard the Demonic Statue of the Outer Path inside. Hagoromo asked Hamura to monitor mankind, a task that was passed to the rest of the Ōtsutsuki when Hamura died. Over time, a civil war broke out between the main and branch families over ideologies, which drove Hamura's clan to near extinction and his message became misguided: if mankind was deemed unworthy, they were to be destroyed.

Centuries later, sometime prior to the Second Shinobi World War, Madara Uchiha summoned the Demonic Statue from the Moon with his Rinnegan, intent on using it to bring peace to the world. In order to achieve this goal, Madara came up with the Eye of the Moon Plan, wherein the Ten-Tails would be revived and its jinchūriki would cast the Infinite Tsukuyomi on the Moon, thereby ending all conflicts by trapping the world in a perpetual dream. Fulfilment of much of the plan ultimately falls to Obito Uchiha upon Madara's death, though Madara is revived in time to see the plan completed during the Fourth Shinobi World War. The Infinite Tsukuyomi is later broken by the combined efforts of Naruto Uzumaki and Sasuke Uchiha.

Two years after the war, the last surviving member of the Ōtsutsuki clan's branch family, Toneri Ōtsutsuki, began moving the Moon toward the Earth so that he could destroy it and rebuild a purer world from the ashes. As the Moon began breaking up in the Earth's gravity and increasingly raining meteors upon its surface, Konohagakure sent a team to rescue Hanabi Hyūga, eventually ending up on the Moon. Toneri was eventually defeated by Naruto and Hamura's actual mission was afterwards explained to him by Hinata Hyūga. Apologetic, Toneri restored the Moon to its previous orbit and, despite an invitation to live on the Earth, stayed on the Moon, vowing that it would never threaten the world again.

Environment
The exterior of the Moon is barren, covered with craters and canyons. It has a weak gravity, but is still able to maintain a breathable atmosphere. Despite its harsh conditions, the Ōtsutsuki were able to settle on the Moon due to their unique anatomy and physiology. To improve its habitability and allow their population to thrive, the Ōtsutsuki built the Tenseigan at the centre of the Moon, granting them light, powering their equipment, and allowing them to control the Moon's movements. Similar to a Dyson sphere, they created a vast environment on the Moon's interior surface, complete with oceans, mountains, forests, and various animal species, however this environment was far smaller than the full size of the Moon itself. The full size is unknown, but its at least as big as a small country. Several villages were built across the landscape, which were steadily abandoned as the Ōtsutsuki's population dwindled.

The artificial sun at the centre of the Moon created by the Tenseigan is actually a barrier, within which are housed various important sites, such as Hamura's shrine, the Tenseigan itself, and a castle where Toneri lives. All are guarded by an army of puppets, controllable without chakra threads because of the Tenseigan, as well as the golem created by Toneri.

There is at least one portal that enables travel from the Earth to the Moon and back. Located underground, the portal itself takes the form of a spring of green water, though contact with the water doesn't leave one wet. By entering the portal, one travels through a dimension filled with various orbs, some of which are earthen in composition, others trap those who contact them in their own memories. At the Moon's end of the portal is the Gatekeeper, a giant crab that prevents unauthorised access. This portal collapses shortly after Toneri's defeat.

Trivia

 * The anime often depicts the Moon as red during significant events.
 * There have been cases that both the tailed beasts and their jinchūriki are affected to a certain degree during a full Moon:
 * According to Gaara, Shukaku's blood-lust is especially strong during a full Moon.
 * In the anime, Blue B, during his time as Gyūki's jinchūriki, noted that he would have trouble sleeping during the nights of the full Moon, because anytime he would stare at it, it would reflect the loneliness in his heart. Gyūki would take advantage of those moments of weakness and try to control over Blue B's body. Blue B was also shown to take sleeping pills to help with this side-effect.
 * An early account of the story given in the series, Hagoromo alone is said to have created the Moon at the end of his life, using it to store the Demonic Statue of the Outer Path so that the Ten-Tails could never be reborn.
 * There are two other known moons that exist in the Naruto universe, both of which are located in Kaguya Ōtsutsuki's dimensions. The first, which is located in the core dimension, was created by Naruto Uzumaki and Sasuke Uchiha after they managed to seal Kaguya for a second time. The second moon is located in the icy realm, and the circumstances in how it was created are unknown.
 * In the anime, when Kaguya first cast the Infinite Tsukuyomi, she used a moon from an unidentified location, by opening a portal to another dimension.