[A demon violently prying open a portal to get home. Previously unknown monsters carrying around bits of monolith-evidence after an energy spike. Pretty compelling, he has to admit.]

So we’re not just talking about a passive connection. We’re talking about the potential to cross a threshold into other worlds or realities.

[Which draws another connection in the overall web: the Singularity, present in this world, harboring the same potential. Whether or not it functions similarly to what Geralt’s described is still up in the air, but it isn’t a so unfounded a guess that they can’t launch hypotheses off of it.]

If the Singularity’s anything like your monoliths, we could be seeing only half of the big picture. A connection flowing in one outward direction, when the reality might be closer to a two-way street. Inbound and outbound.

[A crossroads? It could explain why this world’s magic can summon people from the far reaches of the multiverse, if its nature was at all tied to the Singularity.]

And like the monsters you mentioned, things that mean trouble could sneak in or affect it in ways we can’t see. It’s something to consider if the people of this world can’t figure out why it’s started to weaken, otherwise.