Gaia is a post-Singularity world, abandoned by Humanity when its ruined bio-sphere could no longer sustain Human life. Humanity fled to the sky, populating the Solar System with great habitats. These habitats were not worlds-in-bottles in the sense that has been imagined, but great containers which housed millions of pods. Each pod contains a human body, the locus of their self. Theirs minds are occupied by great virtual-reality worlds, and their bodily needs attended to by dedicated AI-driven machines. These AIs, and not a few crew-members, maintain the ships and an efficient level of population while the greatest minds of Humanity plot their escape from the grip of Sol and their expansion into the galaxy. However, some are not satisfied with the limitless vistas of their artificial lives, and wish to reclaim the Mother-Earth, the Gaia that birthed them.
Rejecting artificial reality in favour of the real thing, these intrepid crews use their resource-stipends to build vast robotic ships they have dubbed 'Titans' after the children of Ouranus, the Sky, and Gaia. Landing in their Titans upon Gaia, they search for the lost riches of plant, animal, and fungal life that were not brought into the Sky by the great arks that fled Gaea when the bio-sphere finally collapsed.
But these crews and their Titans are no more unified than the great mass of Humanity, whose brawling conflicts for resources and power denuded Gaia so long ago. Philosophical disagreements about the general direction of the Titan movement lead to competition between factions, and then outright hostilities. Tiny oases of life have become the focal point of a war over the ashes of Gaia, fought between Titans of metal and meat for the future of Humanity. The War of the Titans, the Titanomachy, has begun.