Dr. Gaia (ガイア博士 Gaia-hakase, alternatively spelled Dr. Gaea) is a Black Ghost scientist, appearing in the Mythos arc of the manga. He developed the Mythos Cyborgs with Dr. Uranus as the Greek cyborg cell for Black Ghost. In the arc, he intends to use his team to punish the "Black Ghost traitors" (the 00 cyborg team and Dr. Gilmore).
Dr. Gaia is a short, balding man with a long dark beard, eyes obscured by shades, and has a large nose. He wears a long white coat.
Compared to the more pragmatic Dr. Uranus, Gaia believes in playing dirty and not showing any mercy to the defectors from the organization.
He believes that victory is most important of all, and plays to Uranus' love of their cyborgs, accusing him of wanting their "children" to be needlessly sacrificed when he suggests a quick, fair fight instead of letting the 00 team be ambushed.
Gaia demands to be referred to with the highest respect, and berates his subordinates often. He often gloats and laughs maniacally.
As a Black Ghost scientist, Dr. Gaia had created the Mythos team, devising them to be much more powerful than the 00 line.
Unlike the 00 cyborgs, who were all still humanoid, the Mythos line had a much broader range of cyborg types, from the giant robotic Atlas to the satyr Pan, with all cyborgs having basis in Greek mythology.
After learning of the Cyborg Men being wiped out in Vietnam, Dr. Gaia and Dr. Uranus sent a telegram to Dr. Gilmore, informing him of their orders to take down him and his cyborgs. Gilmore was given the ultimatum of arriving at Magma Island within two weeks, otherwise the Mythos cyborgs would track them and cause destruction and death to innocent people.
Gaia was noticeably enraged when Uranus suggested that Gilmore might be able to win, and ordered Centaur D to go to Vietnam to take out the 00 cyborg team before they could arrive. Uranus received word from Pan of Gaia's plan for a pre-emptive strike, and Apollo quickly put a stop to it. Gaia proceeded to take Centaur D away for an upgrade.
Later, after the 00 cyborgs had arrived at Magma, 003, 007, and Pan organized a plan for 003 to be taken to Gaia's base under the pretense of her having been captured. However, Gaia quickly became suspicious of the situation, as Hippo Man (in actuality a disguised 007 having taken his form) had supposedly managed to capture 003, while Achilles had died and Helena's Trojan horse had been destroyed.
In addition, one of Gaia's spy seagulls had spotted three 00 cyborgs entering the island. Gaia left his "Mighty Mouse" to spy on 003 and Dr. Uranus, and overheard Uranus figure out the false Hippo Man's true identity. 007 and Pan tried to chase down the mouse, but were unsuccessful.
Gaia proceeded to trap 007, 003, and Pan in an electromagnetic barrier. The cyborgs were later let free by Dr. Uranus, who tried to make it look like a mistake. However, Gaia was on to his intent and threatened to kill him, which caused 003 to convince 007 to go back and rescue him. 007 injured Gaia via a sneak attack involving his transformation, and Gaia complained to his staff about the sudden attack as 007 snuck away with Uranus.
Pan and 003 managed to be re-captured by a Centaur, and Gaia was last seen gloating over 003's captive body and informing the 00 cyborg team that they had 24 hours left to rescue her. He was not seen in any sequences after the cyborgs returned to Magma.
Gaia's final fate is unknown and unsaid, though it can be assumed that he may have been killed in the collapse of his base, along with Magma Island vanishing and plunging into the ocean.
- Dr. Gaia's name is rather ironic in connection to his mythological namesake. In Greek creation myths the primordial goddess Gaia, the embodiment of dry land and the planet Earth, opposed her mate/brother Uranus for imprisoning their children (The Titans) in Tartarus, the land of shadows. She assisted her youngest son, Kronos, in murdering Uranus and freeing the other titans. In direct opposition Dr. Gaia is the ruthless, unscrupulous creator of The Mythos Cyborgs and is opposed by the more benevolent Dr. Uranus.
- Gaia's motivation behind creating the Mythos team was somewhat extended for his counterpart in the 2001 series, and his conflict with Dr. Uranus was altered to be between him and Dr. Gilmore. Gaia was revealed to have mindwiped his cyborgs, believing their human memories to be worthless. He is given a more clear-cut fate in the adaptation, with him being killed by Apollo in vengeance for the death of Artemis.