Necron?

[The Crystal]

So I've heard that Necron is somehow alluded to throughout FF9 (saw it briefly mentioned in another topic). Can anyone please explain this, or tell me where in the game I can expect to find evidence?

In Terra, when Garland is talking about the Iifa Tree. He say that the true form of the tree is not in the physical world.
After Kuja kill your party in the Crystal World, you fight against the true form of the tree(Necron) in the spiritual world. This is why the tree die after Necron is defeated.