Monkey King: Enma was the personal summon of Hiruzen Sarutobi, the Third Hokage. As he was a long-time companion to Hiruzen, it is implied that he is also rather old.
During the Nine-Tailed Demon Fox's attack on Konoha, he fought alongside Hiruzen against the beast. He and Hiruzen also later witnessed the Nine-Tails being sealed inside of Naruto Uzumaki.
Enma was fiercely loyal to Hiruzen, although he didn't always approve of his actions. He kept reminding Hiruzen about actions in regards to Orochimaru. Enma would have preferred to have killed him the first time. Enma was seen in a flashback of Orochimaru's defection, urging Hiruzen to kill Orochimaru, which explains his current attitude. He is also quick to anger, as shown when he tried to break Orochimaru's neck, right after Orochimaru injured Hiruzen.
Enma is capable of using Transformation: Adamantine Staff, which allows him to turn into a large, extendable staff that is as hard as adamantine yet as sharp as a sword, though despite it hardness, Enma has said that Orochimaru's Kusanagi sword can cut him. He can also produce various body parts, such as eyes or arms, from the staff. Additionally, Enma can still move on his own in the staff form, allowing him to return to Hiruzen. Enma can even clone himself in his staff form, turning him into any number of smaller staffs that he uses for Adamantine Prison Wall, a move that can even protect against Hashirama Senju's Wood Release techniques.
Outside of this, he himself is physically very strong, easily handling Hashirama and Tobirama Senju in brief hand-to-hand combat when they tried to keep him from transforming. He also shows knowledge of various jutsu and their effects or drawbacks.
