He thought to himself as he picked up the relatively intact corpses and stored them in pouches, "I guess that the black cape of that guy is made from human skin."
He was referring to the obsidian-skinned man with black eyes. Arthur had some experience with forging Armaments, so he recognized that the man's Armament was from human skin.
For him, the use of a human corpse is to practice turning the human body into an armament in preparation for foundation establishment. It is a need that everyone in the Blood Skull sect has.
Normally, foundation establishment is very dangerous. In a way, it is similar to a surgeon performing an operation on themselves.
In such a situation, there is no anesthesia to dull or eliminate the pain, so the surgeon is going to feel every little bit of the pain of cutting up their flesh.
