It looks like the "gold and silver moons" are actually the images of Venus (?) and the Moon that briefly seem to be racing towards the background galaxy (or maybe that
is the dwarf star Nemesis) before the stage fades out and you enter the battle with the Omega Zone. So between the mother and baby universes, one of them is the stellar object background which fades out as Omega Zone's body appears, and the other is the blobby foreground. I just don't know which is which. What
is clear to me is that
one of them--whichever we should associate with the foreground where Omega Zone drifts (unless the background congealed
into Omega Zone)--is fighting you. Two possibilities:
1. The mother universe resents that it will be displaced by the baby eventually, and so is draining it (starting with Earth) to replenish itself.
2. As I suspect above, the baby wants to achieve physical (or specifically baryonic) reality
NOW, and doesn't care if it has to destroy its mother to attain it. Which it actually
is doing, by
eating the mother (with Earth first on the menu).
I think this might be why the final stage theme is called "Time", as in either scenario, whatever lies behind Nemesis has a low opinion of time. Either the mother hates that the flow of time will lead to its end, and succession by the baby (assuming the mother universe isn't undead already), and so effectively wants to reverse it; or the baby thinks time isn't flowing fast enough.
{frowns} Either way, neither situation explains how the actual Nemesis stage is called "A Mirage of Mind Gaia". I know I hypothesized it should be more like "Hallucination Gaia"--or better, "Hallucinatory Earth"--but I don't know if there's any one kanji signifying "mirage" that I can use to chase down possible words using it. But considering the implicit meaning of the final boss being named Omega Zone--a place where all things end--maybe it incarnates some sort of life-wide death wish? (Leave Philipp Mainländer out of this.) Could be the sort of thing the adversarial universe seized on to begin displacement/absorption. (I should probably look up Japanese words that can translate to "reticent", and find what else they can translate to, in order to circumvent possible Engrish.)
EDIT: At least from Translate Google, "reticent"'s only translation is 寡黙 (kamoku), which can also mean "silent" or "shy". Which does make it sound like the mother universe isn't on the noxious side. So, more potential evidence for the force behind Nemesis being a spectacularly impatient and selfish baby universe.
EDIT THE SECOND: In exasperation, I decided to just set up a list of the kanji Jeffrey's pulled up for "illusion" (no kanji that specifically mean "mirage") and "mind". I'm also attaching the other English words attached to the kanji.
--Illusion:
迷 (Fifth Grade; astray, perplexed, doubtful, lost, err)
夢 (Fifth Grade; dream, vision)
幻 (General Use; phantasm, vision, dream, apparition)
--Mind:
意 (Third Grade; idea, taste, thought, desire, care, liking)
気 (First Grade; spirit, air, atmosphere, mood)
心 (Second Grade; heart, spirit)
神 (Third Grade; god, soul)
衷 (General Use; inmost, heart, inside)
臆 (General Use; timidity, heart, fear, cowardly)
氣 (no classification listed; spirit, air, atmosphere, mood. Variant of 気?)
I just wish I knew how to search for all the possible dyads at once.
Just so we're clear, Jeffrey's is here:
http://rut.org/cgi-bin/j-e/jis/tty/dict