Humanity

This mysterious substance can restore an undead his humanity, granting +2 bonus on all saves and +2 hit points per level until his next death. It is not easy to find, but is sometimes dropped by rats. Humanity is not often sold, as undead are usually unwilling to part with it for any price.

This black sprite is called humanity, but little is known about its true nature. If the soul is the source of all life, then what distinguishes the humanity we hold within ourselves?