PA's got half the riddle right, and everything he has said is completely right. I figured the last line would need some clarification, so here it is.

Out of the two, who is who? <-- All six preceding lines apply to two completely different people in completely separate cases. You have to name both people this refers to and explain why.

Good luck.

edit: Quoting PA for reference. I hate flipping pages m'self.

[q]Okay I have a feeling the riddle might be a completely different style to this (I suspect possibly a line by line deal), but if not I think its about Cait Sith in the Temple of the Ancients.

The person that unravels.
The mystery within. (As one sentence these lines make sense as two the whole Temple sequence, but they're split...)
It crushes him. (Well yeah...)
Nonsense. (Again not sure, there is the scene with Cloud and Aeris etc. that fits here, but I don't know...)
He returns again. (Cait Sith 2)
Out of the two, who is who? (Just a reference to the two Caits)

I think it could work, but again I suspect this riddle is in a completely different style.

Heh, -N- do people actually remember some of my older riddles? THEY were hard , I've toned it down since I think...[/q]
I remember them. >_<