Ah right. I like the duality bit, I didn't think of it like that.
OK. I'll just discard the last line for now then.

Hmmm...duality....duality....that makes me think of Zorn and Thorn. As I can see duality as a term for something in the game. If that was right, then it's an event near Zorn and Thorn. It could have something to do with the Mulitgemini and the Madeen appearance, as that's a more important event with ZnT.

Hmm....let's see.


I am seen,
but I only exist
in dreams of darkness
and beams of light. ------ I think this has something to do with Madeen. Even though Mog is seen, Madeen only comes to life when Kuja's hopes for his evil schemes to work. Or this could refer to Multigemini's feelings towards the characters, as it wishes to kill them. The beams of light refers to the light that comes out of Mog when she transforms.

In duality I am not ---- Madeen appears just after Zorn and Thorn have become one. Meaning that their duality turned into a single entity.

I shine with purple as I am. ---- This could be your interpretation of the colour that blasts out when Madeen appears, or the colour surrounding it's attack.