One of the "Gundam" frames that were produced and used in the Calamity War, roughly 300 years ago. Gundam units like the Gusion are able to achieve a high energy output because they possess two Ahab Reactors. However, because it is difficult to run the two reactors in parallel operation, only a total of 72 Gundam Frames were ever produced. By using the two reactors at their maximum output and combining that with high output thrusters, the Gusion was able to obtain excellent mobility while equipped with super heavy armor.

Although the Gundam Frame is highly versatile and can be used in any environments, the space pirate group, Brewers, customized the Gusion for space use as the group do not intend to operate under gravity. Large propellant tanks are placed within the suit's armor to reduce the risk of the Gusion running out of fuel due to its weight. However, its solo flight distance and combat operational time is still considered to be short. Despite this, the Gusion remains a formidable opponent due to its superior armor that can't be dented by anti-aircraft attacks.