General Garneaux is a high-ranking officer within the Congressional Armed Forces, the military wing of the Congress of Settlement Nations, and serves as the primary antagonist in the Universal Century year 0223. On the surface, he presents a facade of a reasonable and concerned official, appearing to be a leader who cares for the civilian population under CONSENT's governance. In one notable instance, he is even seen having a friendly and trustworthy conversation with the protagonist, Mark Curran, successfully gaining his confidence. However, this public image is a carefully maintained deception. In truth, Garneaux is a ruthless, power-hungry individual who is deeply committed to maintaining his own authority and control at any cost. He is utterly dismissive of the people he is supposed to lead, privately mocking the CONSENT president and his speeches, and he is willing to implement draconian policies to achieve his ends.

Garneaux's primary motivation throughout the story is to secure his power by deliberately worsening a critical food crisis affecting the Side settlements. A scientist named Cynthia has developed a powerful bioluminescent chemical formula capable of solving the food shortage by enabling a massive agricultural breakthrough. General Garneaux, instead of utilizing this discovery, actively seeks to destroy it. His plan is to implement a policy of selective starvation, using the controlled distribution of food as a tool for political manipulation and to solidify his control over the populace. He orders the destruction of the formula and the elimination of those who seek to use it for the public good.

In his role as the story's main villain, Garneaux commands the CONSENT forces in their conflict with the Illuminati, an organization dedicated to peace, and the neutral settlement of Gaea. He is a non-action antagonist who does not personally pilot a mobile suit or engage in direct combat. Instead, he operates from the bridge of his flagship, the Space MS Carrier, where he orchestrates military operations and gives orders to his subordinates. His key relationships are largely transactional and manipulative. His most trusted subordinate and right-hand man is Jack Halle, a skilled mobile suit pilot who acts as his dragon, carrying out his most brutal directives, such as attempting to kill Illuminati members. Garneaux also manipulates Mimi, the fiancée of the protagonist Mark Curran, using her as a spy to track Mark and Cynthia after they escape with the crucial formula.

Throughout the narrative, Garneaux shows no capacity for positive change or redemption. His development is a slow unmasking of his true, corrupt nature, revealing him to be a classic Not-So-Well-Intentioned Extremist whose concern for order is a mask for a lust for power. His fate is sealed during the final mobile suit battle between CONSENT and the forces of Gaea. When he learns that the chemical formula has been returned to Cynthia, he commandeers a Gaea ship in a desperate attempt to retrieve it for himself. In a catastrophic irony, as he orders his men to turn back, a friendly CONSENT mobile suit pilot mistakenly destroys the stolen ship, killing General Garneaux, his crew, and Mimi, who was on board. His notable abilities lie not in combat, but in strategic manipulation, deception, and the ruthless application of military power to achieve his political goals.