General Jiin serves as the primary antagonist. He is the adopted son of the King of Digald, though his ambitions extend far beyond his official title. Originally a citizen of the sky people, he was given to the emperor of Digald to be raised as his own son in an effort to increase the sky people's influence over the empire. However, his intelligence and ambition were vastly underestimated. He eventually turned against his former people, poisoned his stepfather, destroyed the sky city of Sora, and broke all ties with them to wage war against both the land and the sky.

Jiin is a cold, cunning, and deeply egocentric individual who views everyone around him as tools to be used for his own advancement. He is extremely arrogant, believing himself to be omnipotent and superior to all others, and he literally proclaims himself a god. This god complex defines his actions and his treatment of others. He has no qualms about destroying neutral or allied forces who get in his way, firing indiscriminately at opponents without regard for who might be harmed. His ambition for absolute power is so consuming that he eventually stops caring about conquering villages, instead using his personal Zoid to completely annihilate them as a demonstration of his supposed divine power.

His motivations are rooted in an insatiable lust for power, aiming to become the undisputed god of the entire planet. He secretly and aggressively created a new generation of Bio-Zoids to achieve this goal. He is also revealed to have used horrific methods to power his forces, including draining the life force from his own associate Zairin to help produce his own Zoid and using the souls of thousands of his citizens, while they remained fully conscious, to power his fleet.

Within the story, Jiin is the leader of the Digald Empire who initiates a brutal campaign of conquest. He is a skilled political manipulator, carefully managing his relationships with those around him, including his ailing father, to consolidate his power. As his father's health declined, Jiin was entrusted with most of the duties of the state, becoming the unofficial ruler before eventually declaring himself Emperor and then God. He personally assigns talented individuals as his direct subordinates to further his goals. Notably, he befriended the genius pilot Zairin at the military academy and invited him to become his subordinate, though this friendship was always a facade as Jiin saw Zairin merely as a tool to be used and eventually discarded. He also places the young boy Souta under his direct command due to his special ability to activate any Zoid. He gives special preference to his subordinate Felme because she, like him, is a sky person, but he has no genuine connection with her and does not hesitate to try to kill her when she ultimately defects.

Jiin does not undergo a redemption or a change of heart; his development is a steady escalation of his tyrannical and godlike aspirations. He remains resolute in his belief in his own divinity and his right to rule until his death.

As a Zoid pilot, Jiin commands the Bio Tyranno, a nearly indestructible Zoid equipped with the Bio Particle Cannon, also known as God's Lightning, which is the most powerful weapon deployed in the series. The Bio Tyranno is so formidable that Jiin can simply stand still and allow enemy Zoids to land hits on it without sustaining any damage. However, he also displays very advanced piloting skills, capable of defending against multiple Zoids launching surprise attacks. Ultimately, he is killed when the Bio Tyranno is sliced in two through its Zoid core by the Mugen Liger during the final showdown.