The journey is made more difficult by Covenant's bouts of madness from the venomous bite of a Sunbane-spawned monster. Linden, who in this world is endowed with clairvoyance, is frustrated by her inability to help him.
Covenant's bouts of madness, stemming from the venom of a Sunbane-spawned creature, make the journey more difficult for him.  Linden, with her ability to see into the future, is distressed by her inability to help Covenant.