A spiritual leader climbs back down from a mountaintop encounter carrying a written code meant to govern ordinary conduct, moving from the peak experience of direct revelation toward the everyday ground where that revelation still has to be translated into rules other people can actually live by. The image is deliberately about descent rather than ascent, arguably the harder half of any real mystical encounter.
The determined, effortful energy classically assigned to this final decan shows exactly here: revelation is not complete the moment it is received, it still has to be carried, physically and effortfully, back into a world that was not present for it and delivered in a form that world can use. Pisces, so given to dissolving boundaries and touching states beyond ordinary experience, meets one of its more demanding obligations in this degree, the insistence that a peak experience means little until someone does the harder work of bringing it home.
Its weaker form is law obeyed as law long after the living encounter that once justified it has been forgotten by everyone except the person who originally carried it down. The mountain itself is left behind entirely once the descent begins; nothing in the picture suggests a return trip, only the one-way journey from vision back into a life that has to be lived by rules.