The Logrus is not introduced until the sixth book of the Amber series ("The Trumps of Doom"). Merlin's walking of the Logrus appears in a prologue to the initial hardcover edition of the book. We do not see any other instances of a character negotiating the Logrus. The Prologue has Merlin bleeding and experiencing odd sensory inputs. Later we learn that walking the Logrus can leave one mentally unstable for a while afterwards, but this "usually" passes. The Logrus is also described as containing the skeletal remains of those who tried to walk it, but failed.