Three lords rose from the flames and found the lord souls, but the Furtive Pygmy found a fourth, unique soul: the Dark Soul. The pygmy claimed the soul and waited for the fire to subside. Soon the flames did fade, and only dark remained, and thus began the age of men, the age of dark. With his dark soul, the Pygmy separated it into fragments so humans could live.
The humanity item description poses the question: "if the soul is the source of all life, then what distinguishes the humanity we hold within ourselves?" It is distinguised by the fact it was a fragment of the Dark Soul not any normal soul.