Thankfully this is something Bigby does know a thing or two about. He might not know a whole lot about.. well, spiritual energy or whatever, but even he knows about certain natural phenomena. Having wandered all by himself in Europe for a long, long time helped with getting some very personal experience with that, anyway.

"It's supposed to be a natural phenomenon. Something about.. I dunno, light reflections and the atmospheric conditions or whatever."

Don't ask him to explain the technicalities of it. Bigby just knows that it somehow works, and that it isn't magic. That's enough to know, right.

"But it might be something else entirely in this place. I'm pretty sure this isn't the same world as any of us were in before we ended up here." Which means anything is possible. Bigby knows just how huge the differences between worlds can be, after all. Just compare the Homelands to Earth. There couldn't be a bigger contrast.