The darkness and the fear of the unknown made time slow to a crawl, making it impossible for them to gauge just how far a distance they had covered.
The cold and clammy fog swirled around them, condensation on the ropes caused them to get wet and they were soon covered in a thin layer of frost.
The chill from the frost would cause the dampened ropes from the high humidity to freeze easily. After ropes freeze, they become weak. If that happened, they would not be able to hold their weight!
In order to disperse the frost, Jun Wu Xie and her companions had no choice but to infuse their spirit powers into the ropes. Although the the amount of power required to do that was small in amount, but the length of the rope was unusually long and they would need to remain in that state for an extended period of time. For if the rope was to freeze, it would snap off in the middle and the fall would be long and fatal.