Crystal Tower

[seekerofpower]

snip

The story for it isn't released yet, so I can't link you the story, but, as I previously stated, neither of these are a far stretch, as both the Crystal Tower and Valhalla (where Lightening resides) exists outside of normal space time and can connect to all dimensions. There are lots of enemies they could do this with. Ozma and Necron from IX, Zeromus from IV, a creature of the same race as Jenova (as she was an alien and they never say where she came from), any of the Espers from VI (as their village lay in another dimension), Garlemond and Kuja from IX (as Terra lay in a parallel dimension from Gaia in that game), the Elementals from IV (and seriously, who doesn't want to see Rubicante in this game?), Lavos from the Chrono series, the Wave Existence from Xenogears (please SE... Please give Xenogears some love), etc. The list is endless.