In the world of Lower Heaven, the strongest sword is the one that had reached Quintessence. A small glimpse of a Quintessence is said to produce a huge leap in a sword cultivator's advancement.
A single movement of a sword that had reached perfection is a sword that grants enlightenment. Wang Ling's sword was such a sword and as he opened the gate to the World beyond the peak the sword of the Gods trembled in the presence of such a grand figure.
They were but a pseudo-Quintessence weapons, they can never reach the level of the Quintessence without an owner. These swords do not have a soul, but they have spirit and a will. They cannot move around the world of their own volition but they can seek the most suitable owner for them in a ten thousand kilometer radius.