Technology & Combat Characteristics
Despite its legendary status, Gunrex's first combat form is inferior to Neo Zeon's high ranking Machine Soldiers and is easily defeated by Evil Machine Soldier Dark Tyrant. However, Gunrex goes through several upgrades throughout the story. In the manga, it is described as being a machine soldier that grows with its pilot.
History
One of the legendary Holy Machine Soldiers, said to be made in the image of Ishtar, one of Saddrac World's creator gods.
Gunrex was first discovered in the royal family's valley, where it was in a dormant state. The Neo Zeon Clan had captured Cecily, also known as Berah Ronah, as she knows the phrase to activate it. When F91 and the knights of Dabat come to rescue her, Gunrex is activated with F91 taking the controls as the pilot. However, during the first fight, F91 is defeated by Knight Bawoo in Evil Machine Soldier Dark Tyrant. Shortly after, a golden dragon appears and defeats the Neo Zeon Clan surrounding it. After the Neo Zeon Clan's retreat, F91 is discovered to be in a coma.
After many failed attempts by several of the knights to reactivate the Holy Machine Soldier, Knight GP01 becomes the only one able to activate it. As a result, GP01 becomes the main pilot during the battle of Baraba Plains. During this battle, Gunrex is upgraded by the Platnum Shield to defeat Zenon Mansa. However, this it was all a distraction so the Neo Zeon Clan could attack Dabat Castle. Seeing that they need more allies, GP01 goes to recruit the Lacroa Knights.
After recruiting the Lacroa Knights, the group heads to the Gaia Crater to find the Other Holy Machine Soldier, which GP01 and Amuro heard about from Superior Dragon in a dream. When they reach the crater, Gunrex and GP01 fight Holy Machine Soldier Runerex. During this battle, Gunrex evolves and overpowers Runerex, which turns into a ball of light. The light enters Gunrex and it vanishes along with Knight GP01.
Gunrex later reappears in the Pangaea World as the True Holy Machine Soldier, being piloted by Vassal Lord Superior Gundam, which is the combined form of Knight GP01 and Superior Dragon. During the final battle against Rune Carazzo, Gunrex and Superior Dragon sacrifice themselves to destroy Rune Carazzo.