Hmm...
What exactly do you mean by the "structure" of the riddle?
1st line-9 syllables
2nd line-17 syllables
3rd line-13 syllables
4th line-20 syllables
...Nope, no clue there...
(SPOILER)Judging just from the clues, I'd guess that the sun is Meteor. Meteor was alone in the sky doing what it was meant to do-destroy everything.
The grass calling for the aid of the gods would be the land/people in despair at the situation, asking for hope but not knowing if any would come.
The sea healing the earth would be the Lifestream stopping Meteor, though I can't make sense of the cold/hot bit.
The plums then would be the heros or the Shinra. Cait Sith instructed people to take shelter in the slums, as did Rufus and company.
Which would leave the blood to be Sephiroth, and what it did was hold Holy back.
That's the most sense I can make of this. But if I'm wrong, I'll be happy to try again.
