*you begin to climb the creature's back; it's a long climb, at least as high as the Arena's throne. The shadow follows, keeping up. As you reach the small of the back, the creature seems to notice you.
Unable to reach you with its arms, the colossus shakes itself to try to dislodge your grip. The world spins nauseatingly, and you find yourself flung wildly about by inertia and gravity. Your arms and hands ache from the effort of keeping your grip, and you'll probably have a bruise or two from where you impacted the creature's stone-hard skin.
Under these conditions, it's impossible to climb. And below you, the shadow's grip slips slightly.*