Heart of the Mountain (2).
They continued their journey for several hours. The mountains were very big, and their speed of descent was agonizingly slow.
However, they couldn't afford to make any mistakes. The deeper they went, the more chaotic the flow of energy became. At this point, they had lost the ability to use any of their skills. Cain's expression changed from one of worry to annoyance numerous times during their descent.
All this time, the {Dark Soul} kept moving below them. Its job was to notify Cain as soon as it noticed any changes.
As such, they continued to move for hours without rest. Despite his superhuman strength and endurance, Cain could already feel his arms becoming numb.
He was exhausted because of the battle with the {Chaos Orc}, and although he had rested and recovered most of his depleted energy, the recovery was not absolute. He was still rather tired.