Alright, I'm gonna try crack the riddle. If you're saying the reversal keyblade, then I would say it has something to do with Riku from KH1, when he also has a keyblade but is shrouded in the color of darkness, which is an uncomplimentary color. The battle was also fast, and he did have moves were he moved extremely quick like lighting. It was drawing to the end of the game, and after the battle they were transferred to an area of pure darkness, where they fought a beast. Climax? That's when Sora finds Kiri, and he fights Riku. This must be right! A stream of lines (Princesses gathered?).

This is what I think, i hope I'm right.