I'm not sure which thread to post this on... But since here is one of the more meta-forgiving threads we have, I'll try it here.
I just had a very creepy hunch a few minutes ago:
What if sealing the wall kills the characters on this side?Let me elaborate: They are not from this world. They are from the other side of the wall. They do not exist here and that we can craft a power vacuum to whisk them away, means they're somehow still linked with the things there. Think fishing rod. We have the hook here, but the rod itself on the other side. Sealing the wall severs the line, cutting the connection, meaning, the hook will sink.
But, that wouldn't be an issue... What I think should perhaps be compared to water and oil. They, being from another reality, are not exactly the same as us. What is different is undefined, but something is, or we'd not have a crisis on our hands and inter-universe travel would be a thing. So, suppose you put water and oil together... They'll not mix. It creates a layered texture, so, to make it "stable" as in "homogeneous" you could apply movement. Shake it up. Put it on a blender and let it mix so that it's a single texture. They'll be a single composite as long as the blender is on. But turn it off and, even if the water stabilizes, the oil will get ejected from it.
We have the Wall open, the "tremors" Mr. A has said, the crisis itself... This open link to the other side is shaking our world, but it is what is keeping the characters stable within our world. Seal it off, stop the tremors, and they have no more sustenance within our reality, thus, get kicked out. Since the way home is closed, they'll just get ejected to the nearest open spot, wherever that is, which is what I call as "death" for the sake of this idea... (Or in a case similar as Pan's case noted bellow they might simply stop existing, vanishing completely).
Don't bring physics into this, please?

As Pan vanished in a spark of light and we all know matter does not vanish like, and if the atoms that should compose his body were to turn into gas... Well... Anyone that can talk physics on this level should be able to calculate the energy levels of such a process. Besides, the fact that it happened seems to prove that they're not built from this world's matter, thus, do not belong here from a physics view. And since they exist and interact, they are sustained
somehow that is not fit within real world physics. We can either Meta-Handwave or see this as evidence that they are not really the same as us.
As to meta... Remember Dryu's argument that since they're not here being played by the GMs and all that, that they can't stay here no matter what happens in the end? Well, if they cease to exist once the link to their world is cut... Well... It gets rid of them just as much as reficking them does. Only it's 'killing' instead of 'sending them home'. If so sealing the wall is perfectly fine, and even easier, as long as we're willing to kill them.
As I said, this is just a hunch, a creepy thought that crossed my mind minutes ago, so don't think I'm saying this as an end all theory or anything of the sort. I barely had half an hour between thinking his and pressing submit, so...