It's a blog! Mainly of book reviews.
The guide says they are getting near and then says, I'll cover for you if you just run away! Of course, Gawain won't have that so the guide tells Gawain where the Green Chapel is, refusing to go any nearer himself. Gawain wanders on and finds a grassy mound that might be the Devil's chapel.
It's obviously a burial mound, which according to folklore marks an entry to the land of Faery.