A clarification to what ultrafilter said – the plot of the movie is completely different from the games, but the ideas about nature, life, and death are similar to two of the games – FF7 and FF9.
Start with the idea of the Lifestream from Final Fantasy 7 – a sort of idea of reincarnation in which rather than one soul transferred from life to life, all souls of all living things return to a common pool at the moment of death, and new souls are created from that common pool.
The Lifestream – the place between lifetimes – is a sort of paradise, in which souls are one, until parts of that one split off to give life to plants and animals. The lifestream is depicted as a sort of liquid-blue energy in FF7, and the lifestreams of different worlds in FF9 are shown as blue and red.
Also add the idea that an entire planet is a living organism, of which life on the planet are the cells.
They are “waves.”
Think of Gaia and the original world the phantoms inhabited as two incompatible computer systems. The two life forces were incompatible. The scientists were trying to make them compatible.
They cannot construct or alter these energies from scratch. They must find them. They are trying to construct a series of patterns that will neutralize the phantom life force by converting them into a format that can be absorbed by earth’s Lifestream.
Essentially. They were trying, and failing, to join the lifeforce of our world, the process of life and death, by blindly reaching out and grabbing at the nearest source of life – whether human or animal. Because the “programs were incompatible,” the “data” was corrupted – the souls/lifeforce of these people destroyed
The alien Gaia was converted to a format usuable by our Gaia. Both were made happy because the alien Gaia was no longer flailing stupidly around looking for a chance to be reborn, and the earth Gaia is happy that it is no longer being torn to shreds by the phantoms.
They are now one and the same. The souls of all alien lifeform – plant, animal, and humanoid – will now be born on earth as earth creatures. The memories and experiences of that world may continue to appear in dreams, etc.
Gaia wanted to find the 8th spirit because if it didn’t, the alien Gaia would kill it while trying to join with it. Not sure what it meant about the 8th spirit being within her.
Somehow it got inside her, trying to fuse with her – in the process it would inadvertantly take her soul/lifeforce. They contained it. It doesn’t want to kill her, but being an undead soul, it’s not really all that smart. Stimulus-response. It sees lifeforce, it moves towards it.
Yes. He is dead but his soul is not destroyed. It’s rejoined the common pool, and his sacrifice means that earth won’t become the next dead planet. He will be reborn as something else, or perhaps several something elses. The two worlds have become one.