They're falling? They're falling. Peridot is distracted by the increasingly intrusive sounds of clashing fae, AND she's sitting on Lambert's shoulder again, so. She doesn't notice the ground giving out, until they're all already on their way down.

Reaction already delayed, the gem squawks as the earth swallows them up, naturally assuming that this is not a part of the plan, and that some kind of vicious subterranean fae must be trying to trap them. She puffs out her fur and digs her claws into the witcher's shoulder, and frantically casts out with her metallokinesis for something to hold on to, anything to arrest their descent with. Fortunately, she is already perched on a significant source of metal...

So, this is how-- despite it not being a very long or particularly perilous fall-- Peridot and Lambert both wind up stopping very suddenly and late into the descent in mid-air, and remain hovering a few inches above the tunnel floor, suspended by a combination of Peridot's powers and Lambert's metal skeleton.

Still spooked, Peridot casts a round eyed stare around at their companions, trying to figure out what just happened.