Despite the fallen god's malevolent and powerful aura, Andrew and the others stood firm and defiant. The fallen god wasn't too pleased, as he was used to having their presence inspire fear.
Even so, he didn't flinch and simply said in a low, yet grave and threatening voice, "Ignorants, even if the three you left outside joined forces, they wouldn't be able to defeat me". He was obviously referring to Terra and Aqua's sisters, who remained behind to protect the seal and prepare for a backup plan in case Andrew and the others failed in battle.
The fallen god's words weren't false in a way. It's true that he is much stronger than all of them combined, but that would be if he were in full form, or even if he were in the outside world.
In the separate space, within the seal, things were different. First of all, there was only the soul of the fallen god here, which, while corporeal, is still only an artificial body, not his true body, so its strength is only half of his true self.
