The Gang has to cross the large chasm called Cleavage Ulteros, or they won't be able to deliver Mishral Arden's letter (and will end up dead again). Could the mushrooms be key?
Also, Ash mentions a "rosy cheeked young lad" during the recap.
The Gang woke up dead with no knowledge of their names, with Death offering them a quest to deliver a letter to Mishral Arden, in return for their very lives. And the clock is ticking - they only have a few days to do so before they die permanently!