A mysterious mobile suit that exists outside of history in the G: Universe. Gundam Latreia was created by Code; Maxwells as its "Gundam to surpass all Gundams" as part of its "Theos Program" plan. Aside from its high specs, the Gundam is equipped with an array of beam weapons. The machine can transform into its Pheonix Rider mode and ram into enemy units. It was also developed to serve as the core unit for the mobile armors Plugin P to become the heavy bombardment unit Pneuma Bull and Plugin H to form the aerial fortress Uios Sky. Its final form has it combine with both to form the giant Gundam Theostrias.

The Latreia drops its beam rapid guns and transforms into its MA mode while wreathed in fire, ramming into opponents before somersaulting upwards and crashing into the ground with a fiery ground pound with its fist.

The Gundam Latreia is first encountered in a Break Mission pertaining to the Sanc Kingdom incident, piloted by Hermes Mercury, but is forced to break out. It began making sporadic appearances throughout G: Universe's database, sometimes as an ally (as Hermes) and other times as an enemy (as Maxwells). During later appearances in Break Missions, it would be supported by mass-produced copies nicknamed Mysters. In each Garbage Space encounter between Directories, the Illion Stable crew discover mobile armors with the same code signature as the Latreia, with the mobile armors later displaying the ability to dock with the Gundam Latreia to become more powerful. After a clash with the Uios Sky, Sakura Slash and Juno Astarte manage to pry Hermes from the administrator's control, and Code; Maxwells takes full control of the machine.