The air was different, too.

It was very still.

Under their feet at times was a wonderful carpet of soft moss in which Thor sank nearly to his armpits.

And the forest was filled with a strange gloom and many mysterious shadows, and there hung heavily in it the pungent smells of decaying vegetation.
Thor did not travel so swiftly here.

The silence and the gloom and the oppressively scented air seemed to rouse his caution.