I was hit by a stray thought while reading. Wondering if B-Money has commented on this, or if my understanding is flawed.
My theory is that Nightblood could have potentially world-ending consequences, if they were thrown into the Lumar spore seas. It is unlikely that it would drain all the seas immediately. Brandon has mentioned the investiture food-coma before, however Nightblood isn't going anywhere, and we know that they'll be hungry again at some point.
Furthermore, it seems that no Lumarians have the technology to dive down and get it up once it sunk to the bottom(disregarding the known world hoppers)
The only thing that seems to speak against this is whether Nightblood can access the investiture. We know it doesn't have to be kinetic, but potential investiture is still kind of vague
PS: Obviously not all of the seas would be gone