Why don't I remember Gilgamesh being in IX? D'=
He was the
four-armed man
He doesn't have fakes.
Yes he does.

The kanji reads "fake"


Chocobo on the blade. No chain on the end. No trigger.

Has two hooks on the end instead of one. Blade is much more translucent. Hilt is slightly different. Need I go on?
Anyway, aside from XI, it's the same Gilgamesh. He passes from dimension to dimension via The Void. He talks about it a bit in VIII. I can't be bothered to go into more detail, look it up on your own.