Hashirama's Artificial Body

is a non-sentient clone of Hashirama Senju created by Madara Uchiha in order to harvest his unique Wood Release kekkei genkai. It is located in the underground section of the Mountains' Graveyard, and was grown using the Demonic Statue of the Outer Path's power as a catalyst.

Appearance
The clone, which naturally bears strong resemblance to Hashirama, grows out of the side of a giant flowering tree, with eight hands suspended around it. The stem, which grew noticeably longer by the time Obito Uchiha showed the tree to Kabuto Yakushi, bears a single flower, upon which the Demonic Statue sat among its petals. The tree also has spike-like protrusions, which jut out from around and along the its stem similar to branches, and a gigantic network of roots extending into a massive flooded cavern.

Role
When Madara fought Hashirama at the Valley of the End, the former was believed to have been killed. In reality, Madara used the battle to collect Hashirama's DNA and negated his own death through the use of Izanagi. Madara later used the Demonic Statue of the Outer Path to cultivate Hashirama's DNA, which resulted in the creation of an enormous flowering tree containing a clone of Hashirama. To extend his life beyond his natural lifespan, Madara continuously took in the Demonic Statue's chakra by attaching himself to the tree using three tendrils that extended from its stem. A number of developing White Zetsu appeared on the tree's branches, leading Madara to believe they had been created as an unforeseen result of his experiments, when in actuality they had secretly been removed from inside the statue by Black Zetsu.

When a mortally injured Obito Uchiha arrived in an underground tunnel connected to Mountains' Graveyard, Madara had the White Zetsu retrieve him and attached Hashirama's artificial body to his damaged right half. Prior to his death, Madara placed some of his will into the tree in the form of chakra receivers, which later protruded from the Demonic Statue's navel. By the time of the Fourth Shinobi World War, 100,000 White Zetsu had fully developed. After Kabuto Yakushi captured Yamato and used him to further improve the White Zetsu, he suspended him in the tree's stem, facing Hashirama's clone.

Trivia

 * In the manga, the flowering tree is entirely white in colour, whereas in the anime, the tree itself is brown and the flower on top is purple.
 * Overall, the tree and flower resemble the golden lotus flower with a much longer, thinner stem.