Okay, my critique for Sie, since my writing is still going slowly...

It's action-packed, to be sure. It does seem a trifle difficult to keep Lightning and Altair in character, especially since it's been my estimation that neither one of them has ever been blessed with an abundance of personality - mostly they're cold-blooded killers. Most of what you wrote centers around the battle itself, which is probably for the best. You did mention from the "perspective" of Altair, however (this is assuming that his train of thought is leading the narrative), that Lightning's garb was typical of Final Fantasy, which leads me to ask how he would know or be aware of her universe, or that it has that specific name. On the other hand, you did say you had a plan for all this, so I'll wait and see what it is.

Other than that, and minor grammatical mistakes here and there, it's a fun read. Keep it up!

And I think I'm going to change my format a little bit for my posts. I'm already very late with my prompt (I know it was supposed to be a weekly thing) but I'm not going to give up on it. I'm going to make it a little more creative than before. Keep an eye out!