Xam'd

Xam'd are depicted as a mysterious type of being related to what is referred to as "Humanform Weapons". The first Xam'd shown in the anime series is the form that Akiyuki Takehara takes after a strange light enters his body during an apparent suicide bombing on a bus on his native Sentan Island. In the wreckage of the bus, the "bomber" (Nazuna) touches his forehead, where a red gem appears, activating the Hiruko within him and causing a 'mask' to appear on his face. Transformed into a Xam'd, Akiyuki is mistaken for a Northern weapon, a Humanform.

Xam'ds' and Humanforms' forms appear to be made of a combination of organic and mineral elements, though they do not appear to be strictly one or the other.

When Xam'd suffer physical or psychological damage, they begin to crystallize and if uninterrupted, the crystal growth will cover them completely and they will eventually turn to stone. Other living things caught in this process will also be overtaken and turn to stone;  Nakiami has had close calls with this several times.

Both Xam'd and Humanforms are created by instilling or implanting Hiruko into a human host, and are referred to by some characters in the series (e.g./i.e. Nakiami) as "symbiotes". The emotions within the human host and the Hiruko symbiote are always struggling to become in tune with each other, and it is easy for the human host to lose their identity to their own emotions, given power by the Hiruko, and to the emotions of the Hiruko within them. Any emotional imbalance or loss of focus can cause the host to be overcome by madness (see "Furuichi Teraoka"), often the catalyst of transformation, and causing the Xam'd or Humanform to completely lose themselves and wreak havoc on their surroundings. Nakiyami takes it on herself to train both Raigyo and Akiyuki, with the help of Madam Tenshin, to retain their humanity and develop a harmony with their Hiruko symbiote.

It is revealed by Sannova that the Xam'd were created to oppose the Hiruken Emperor, in the hope of one 'complete' Xam'd forming, and ultimately defeating him. When a Xam'd becomes complete, becoming at one with their Hiruko, the gem on their forehead turns blue. Raigyo had already accomplished this before Akiyuki met him.

List of Xam'd appearing in the series
Akiyuki Takehara

Furuichi Teraoka

Raigyo Tsunomata

Kujireka

Yango

Giant green Xam'd

Hiruken Emperor