So if that's the case, how come Igneel or any dragons that entered the Dragon slayer's body didnt tell what that seed could do? And that you can just get rid of them by "i am human"? Can it only be removed if you've got demon and a dragon seed? Do they not know the seed's existence? if not, how does Natsu's dream knows that there are two seeds inside himself, and it takes "i am human" to erase them?
These questions probably makes me sound very dumb but I just wanted to get clarity on the Seed stuff.