The Myriad Ancestor Sword is one of the two extremely powerful Godslayer Artifacts which have existed since ancient times. It was controlled by the Ancestral God Land, making them one of the most powerful forces in the Draconic Ruins Realm. While the other Godslayer Artifact, the Sacred Demon Blade is controlled by its enemy, the Ancestral Demonic Saint Land.
During an ancient great battle, the sword was separated into seven pieces. The Ancestral God Land holds one section, while each of the six divine sects holds the others. In order to keep this important treasure hidden, typically only the strongest Martial Ancestor Realm expert will know of its existence and stand as its protector. Only passing it to another when they are about to die. Within the current Divine Feathers Sect, the one protecting it is most likely Hierarch Martialsky.
After recovering her memories, Yu Yan believes that only the Myriad Ancestor Sword could be powerful enough to break the seal on the Tiny World. By breaking the seal placed by the World Creator, the Tiny World would no longer be protected. Though this is dangerous, she believes that they must hurry to find the Temporal Demon Spirit Book, which is hidden there. The Myriad Ancestor Sword can conceal the aura of the Temporal Demon Spirit Book after they find it, protecting it from the Sage Emperor.
During Nie Li's visit to the Heavenly Note Sect, he exchanged the fragment of the Myriad Ancestor Sword of Nangong Xianyin for 5 Sacred Elixirs hundredfold more effective than those they had already receive from Ye Ziyun and Xiao Ning'er.