When Sumo first tries to enter the cave, he is spit out by an entity called Gaia who tells him that he shouldn't walk into his mouth. He later learns from the dwarves inside Dwarf Cave that Gaia likes silver, and he will let anyone through if they are wearing silver stuff.
Once Sumo has obtain the silver equipment, he ventures through Gaia and comes out in the western land. As soon as Sumo walks out, he's stopped by a voice from behind. Bogard comes up from behind, telling him that Cibba told him about Fuji being taken by the Glaive Empire. Stating that Julius is good at disguising himself, but there's a chance of rescuing her because Glaive's Airship is refueling at a lake up north. Afterwards, Bogard joins Sumo.
Gaia was the goddess or personification of Earth in ancient Greek religion, one of the Greek primordial deities. Gaia was the mother of all: the heavenly gods, the Titans and the Giants were born from her union with Uranus (the sky), while the sea-gods were born from her union with Pontus (the sea). The Greek word "γαῖα" (transliterated as gaia or gaea) is a collateral form of "γῆ" meaning Earth. Her equivalent in the Roman pantheon was named Gaea (Terra in more ancient documents). This is alluded to in Final Fantasy IX with the existence of Gaia's twin world.
The mythological name Gaia was revived in 1979 by James Lovelock, whose Gaia hypothesis proposes that living organisms and inorganic material are part of a dynamic system that shapes the Earth's biosphere, and maintains the Earth as a fit environment for life. In some Gaia theory approaches the Earth itself is viewed as an organism with self-regulatory functions. This theory is especially alluded to in Final Fantasy: The Spirits Within's take on Gaia as the planet's soul.