Final Fantasy

You flip the Final Fantasy book around a few times, trying to figure out the secret of the lost tales within. After a few times, the cover seems to shift to the back as you hold it upside down, the title of the story changing from "Final Fantasy" to "The Last Story". Numerous tales dot this side, far more than the front, each of which the story of how a world became destroyed and devoured. So many worlds lost... The good news, it seems, is that a vast majority of these stories seem to have been a result of Chaos gaining a large momentum early on that each world's resident heroes couldn't recover from. You know that's not been the case here... Looking at others... Chaos has not been above stooping to trick a world's heroes into destroying their own crystal(s) in order to grant it strength. Not really the case here, either.

You delve a bit further and find tales of where heroes confronted the evil possessed by Chaos in their worlds and still lost. It seems it regressing into his original form is rare, but it has happened. In those cases, however, it seems Chaos was actually forced on the back foot a bit, though was able to win in the end as heroes put their guard down. The creature is capable of everything from powerful blitzes of magic, rending physical blows, psychological attacks and barraging waves of status ailments. Its appearance as a demon would likely suggest an affiliation to Shadow, but this isn't actually the case. Chaos is unaffiliated with any particular element, which is... somewhat troublesome. At least sealing Lich must have thrown this creature into some sort of imbalance, however, perhaps giving it weakened Earth affinities? This weakness is also unprecedented, but you shouldn't let it put you at ease, either.

You may have handled the others well enough before, but as far as 'psychological attacks' go, the book seems to imply that in desperation, Chaos can alter the perception of reality of those it fights. It is no illusion, but the power of chaos creating subjective reality that causes his victims to experience entirely different lives and lose the will to fight. If Chaos has the power of a Crystal on his side, he could even rewrite an entire world's history this way and have it take to favor itself.

Finally, you recover a bit of information from chapter 8 of the original side that you've been told before, long ago, by a certain Renegade I think, but a refresher is never bad. It seems that sometime long after the events of the Time Compression, a group of Terrans would seal Chaos into the core crystal of their world to prevent it from escaping. Perhaps this too was incentive to keep absorbing worlds... or perhaps Chaos itself was shortening the lifespan of Terra to force their hand and grant himself freedom. In any case, when Terra's crystal attempted to merge with Gaia's, that being too became part of the world. And when Kuja broke that crystal, the weakened Chaos was freed, confronting Zidane and the others in the form of a being representing Death. At this point the Fiends were awakened as well, (though Tiamat was a bit of an exception to that as she mentioned before, so it seems the seal wasn't absolutely perfect either way). The Cloud of Darkness too, began moving forth to spread its despair.

It is perhaps also thanks to the Terrans who created the guardians in the likeness of Fiends that lead to Chaos regressing. Or it could be that Chaos was trapped for so long that it began to weaken considerably. ...In any case, it's almost certain this is what this is. Chaos is weakened in an unprecedented way and forced on the defensive, but should still not be underestimated.