Theodor Harvey was born to Kluya and Cecilia. While growing up, he always wondered why his father was fascinated by the moon and was unaware of his father's origins as a Lunarian.

His father would not tell him until he had mastered the arts of magic. Theodor boasted that he can cast magic, but when his father asked if he's even mastered the Cure spell, he admitted he can't. When Theodor returned home afterwards, he saw his mother collapsed on the floor. She told him she was alright, and that she's just tired from carrying her next child. Excited about having a brother, Theodor went to bed.

Later, Kluya was attacked by the very magic he had taught to humans. When Kluya wondered if it was right to teach the people of Earth magic, Theodor assured his father it was, comforting his father in his final moments.

As Kluya passed on, Theodor tried to cast Cure on him, but was unable to. The villagers of the town took care of Theodor and Cecilia afterwards, and when Cecilia finally gave birth, she died in labor.

Unsure what to do, Theodor took the child and ran away. As he fled, he heard a voice telling him that the baby was the one responsible for taking his mother and father away from him, and that he was worthless for letting it happen. The voice then told him that he was "an insect born from a dragon's corpse", and declared that his new name was Golbez. The infant grew to become Golbez's brother Cecil Harvey.

In reality, the voice was Zemus. Taunted by Zemus' voice and ashamed of his actions, Golbez fled civilization. Eventually, combined with Golbez's Lunarian blood and his hatred of his younger brother, Zemus was able to influence his mind and take control of him. Golbez subsequently lost many of his memories and began to gather the Crystals to summon the Giant of Babil.

The Giant would then depopulate the planet so that the Lunarians, presumably under Zemus' control or command, could live there rather than stay in stasis inside the moon.

Taking control of the four Archfiends sent to him by Zemus, Golbez has Cagnazzo assassinate the King of Baron and impersonate him, using the Red Wings to steal the Crystal of Water from Mysidia. However, Cecil, Lord Captain of the Red Wings, is hesitant over his orders and is removed from duty when he returns and questions the King's actions.

Golbez takes his place as commander and attacks Damcyan, stealing the Crystal of Fire in an attack that killed a young woman named Anna, daughter of a powerful sage, Tellah. In response, Tellah swears revenge against Golbez and sets out to kill the sorcerer at any cost. Meanwhile, Cecil assembles a group of allies, including Yang Fang Leiden and Prince Edward von Muir of Damcyan, and heads to Fabul where the third crystal is kept.

With the warning from Cecil and Yang of the impending attack, the King of Fabul tightens the defenses of the castle, and Golbez is eventually forced to enter the castle himself with Cecil's friend Kain Highwind, who he has taken control of telepathically.

With Cecil wounded by Kain, Golbez effortlessly strikes down Yang and Edward, taking the Crystal of Air and also kidnapping Rosa Farrell, the woman with whom Cecil and Kain are both in love.

After this, Golbez takes all three crystals to the Tower of Zot. Once he receives word Cecil is attempting to climb Mount Ordeals and become a Paladin, he dispatches Scarmiglione to kill him. When this fails, Cecil then returns to Baron and kills Cagnazzo, restoring Baron to the peaceful nation it once was. However, Golbez had already stolen the Red Wings and placed Kain in command.

Kain rendezvous with Cecil and offers to return Rosa if Cecil brings them the final Crystal from Troia. Cecil retrieves the Crystal from the Dark Elf and brings it to the Tower of Zot.

Climbing the Tower, Cecil hands over the Crystal, but Golbez refuses to return Rosa. Enraged, Tellah pushes Cecil aside and confronts Golbez. After fruitlessly casting his best spells, Tellah sacrifices his life to cast the ultimate magic, Meteor. Although Tellah dies shortly after, Golbez is severely weakened and his control over Kain is broken.

Golbez retreats, and strikes down Cecil when he attempts to follow. At this time, Golbez apparently recognizes his brother, and hesitates to deliver the finishing blow. Although Cecil is confused, Golbez announces he will destroy him at another time and leaves the tower.

Afterwards, Cecil and his companions enter the Underworld, where Golbez has already gone to find the next four Crystals, of which he already has two. After defeating his minion Calcabrina in the Dwarven Castle, Golbez appears and tells Cecil his plan. Cecil and his friends attack Golbez to no avail, and Golbez summons a Dragon to kill them. Rydia intervenes with her Mist Dragon, defeating Golbez's dragon, and with her assistance Golbez is defeated. However, he is again only weakened and manages to take the crystal before escaping.

After this, Golbez does not appear for some time, until he takes control of Kain again in the Sealed Cave and has him take the final crystal. With this, Golbez activates the Tower of Babil to call the Giant of Babil. Cecil and his companions in turn retrieve the airship known as the Lunar Whale and go to the Moon, where they meet Fusoya who tells them that Zemus is controlling Golbez and returns to Earth with them.

On Earth, the Giant begins its attack, and with the help of the combined forces of the Overworld and Underground, Cid Pollendina flies Cecil and his friends into the Giant. After destroying the Giant's core, Golbez emerges and Fusoya shatters Zemus' control of him. Golbez promptly remembers who he is, surprising Cecil with the knowledge he has been fighting his own brother. Golbez and Fusoya leave to go to the Moon and defeat Zemus.

Following them, Cecil and his companions find Golbez and Fusoya battling Zemus. Although they easily defeat him, Zemus is quickly reborn as Zeromus, and their attacks fail. Golbez uses a Crystal to try and turn the tide, but as he has lived a life of darkness he fails and Zeromus strikes them both down. Golbez then gives the Crystal to Cecil, and he and his companions are able to use it to make Zeromus corporeal and defeat him.

After the battle, Golbez confronts Cecil with calling him "brother" before the battle, although Cecil does not respond. Realizing that he is unforgivable for his crimes, by Cecil and the people of Earth, Golbez decides to go to the Lunar Sleep with Fusoya. He leaves, but Cecil calls out to him and says goodbye before he does, indicating he may forgive him after all.

Soon after this, Cecil ascends to the throne of Baron, and the Lunarian's moon leaves the earth's orbit. Cecil receives one final telepathic message from Golbez, saying good-bye.