Batman can feel Frisk's fingers digging into him, but it doesn't really hurt, even if there's a distinct pulling sensation. His grip will briefly tighten, however, just to make sure they aren't slipping or anything, before he resumes focusing on flying.

The cloud cover is definitely a bit of a visibility issue- but being the Batman he can at least get a vague idea of where the rocks are, even through all the fog, just from listening out for the faint echoes that bounce off of them. Frisk won't have to worry about them crashing into the sides of the cliff, at least.

He circles slowly further and further downwards, around the enormous cone of rock jutting beneath the castle, flapping his wings occasionally to change direction or to keep their ascent at a reasonable pace. After a few minutes he'll tilt his head to glance over at Frisk.

"How are you holding up?"