9 perhaps has the most complex story, and this just leaves me more confused I think.

the whole "Terra exists in the core of Gaea" and the FUSION spell are two things I don't seem to remember from the game. Most people on Gaea were wiped out when it was first attempted? I'm guessing all the civilizations slowly built themselves back up again? I also thought the Terra you visited was like an artificial recreation of it where Garland could plot/wait out for his plan to be completed. I don't know.

Playing FFIX always gives me the feeling that this game is somehow trying to tie together Crystals, Summons as guardians, Garland, people from "Red" planets trying to assimilate w/ Blue ones, and Life returning to the planet to establish a connection throughout the series. But once you start getting really far, it seems that it doesn't do that. I don't know.