(not including the wings)
A humanoid super weapon born from an egg that was in the underground ruins of Tokyo. It looks as though it is in the image of a god with no weapons that are particularly visible on its exterior. It is a being to be feared with the ability to manifest supernatural power, such as emitting light from its palms.
The RahXephon is a bipedal humanoid mecha. It is several stories tall, immensely strong, and capable of unassisted flight. Its offensive capabilities include energy blades which project from its forearms, and an energy bow. It can also form energy shields around its forearms, and create impenetrable spheres of energy in its hands which are used for carrying and protection.
While dormant, the RahXephon's face is shown covered by a pair of large wings which are attached to its forehead; these wings separate and spread when the RahXephon becomes active, and appear to be tied into its overall function. Its forehead features a golden disk, alluding to the sun god Ra and Ollin Tonatiuh. Its eyes are normally red but are occasionally golden with visible irises; it also has a pair of smaller red eyes on its visor. Below its face is an egg-shaped protected barrier which Ayato is absorbed through when entering; he is then dropped through another barrier into the pilot's seat, which resembles a pair of cupped hands emerging from a seemingly endless pool of dark water and contains two control rods.
The RahXephon is connected physically, mentally, and emotionally to its instrumentalist. Its arms and head mimic Ayato's movements. The field of view from the pilot's seat is a grid of hexagons which follows Ayato's view; the RahXephon's shields also have a hexagonal grid shape. Ayato is shown to be absorbed into the RahXephon in a variety of manners, and it moves on its own to meet Ayato several times. Ayato can also trigger awakening and entering the RahXephon through voice command. Ayato appears to feel damage inflicted on the RahXephon as physical pain. During the battle with the Dolem Forzando, the RahXephon is pierced through the shoulder with a spike of debris; Ayato is shown in the cockpit holding his shoulder in the same place shortly thereafter.
It is revealed that the RahXephon was created by Ernst von Bähbem as a tool for re-tuning the world. This re-tuning would involve the RahXephon joining with a special person who has the potential to accomplish the re-tuning, referred to as an instrumentalist. The Mu refer to the robot as "Xephon," only adding the honorific of "Rah" near the end of the series when Ayato is ready to tune the world. The RahXephon's TERRA designation is the "5-A" OOPArt or "Mulian Artifact Class 5 A (MA-C5A)". In the show the name of the RahXephon (ラーゼフォン?) is sometimes written in Chinese: 翼神世音; pinyin: Yìshén Shìyīn; Wade-Giles: Ishen Shihyin; a literal translation of this is Wing-god World-sound.
In the manga, the RahXephon is an artifact mysterious even to the Mu, used in a ritual that grants the desires of its occupants.