Thanks to IkariLoona for the inspiration!
Gilgamesh first appears in Final Fantasy V. When we first see him, he has two arms, but then in the void, he has for more. SIX! Why? How did he get them? Little known fact about Gilgamesh: he’s one of Ex-Death’s monsters. He’s retroactively human in later titles, but even so in Final Fantasy VIII, he has four arms.
As for an in-game answer, I don’t know why he has some many arms. I’m even more confused as to why we’ve never known about them until late game. He probably always had them tucked away. Perhaps strange things happen to those in the Void. Maybe Gilgamesh grew arms in the Void? Perhaps the Void enhances physical characteristics of monsters.
Or rather, it was a part of some Deadpool-esque joke. Maybe we were to feel anxious fighting Gilgamesh’s true and final form. Gilgamesh can be a difficult boss battle with only two arms, but six!? We’re in for it now, right? Only, the battle becomes a bit anticlimactic. I think that’s the joke, something happens about Gilgamesh that we weren’t expecting. This is one of the reasons he’s such an exciting character in the franchise.
Whatever the reason, Gilgamesh uses fake cardboard arms in Final Fantasy. What happened to them? IkariLoona suggests:
Gilgamesh uses fake cardboard arms in FF8 because he got some of his chopped off somewhere along the line during his multiversal travels – just because 8 was his 2nd game doesn’t mean it’s not one of the final events from his point of view.
How did this happen? Was he fighting for a sword? Maybe they fell off, like a lizard’s tail? And where in his timeline does Final Fantasy VIII take place? Perhaps we have yet to know the answer, as Gilgamesh is still hopping around in the Void.