The Heavenly Sin Divine Sword or also known as the 'Monarch of Swords', is the only known Sovereign Profound weapon in the Profound Sky Continent. Because of this sword the Mighty Heavenly Sword Region framed and exterminated the Eternal Night Royal Family.
There's a rumor that who ever can control the sword would be unrivaled in the Profound Sky Continent. Its current whereabouts are unknown but the most popular theory is that its already in the hands of the Mighty Heavenly Sword Region. 
Later it was reveled that it was in fact the Mighty Heavenly Sword Region that obtained the sword and there is a Devil Spirit that has been sealed within the sword by the Evil God, and Xuanyuan Wentian from Mighty Heavenly Sword Region is plotting with the Devil Spirit to get Fen Juechen's Devil Blood in order to release the it, in exchange from world dominance.
It was eaten by Hong'er.
It's true name is Eternal Night Devil Sword.
- The Devil Spirit that is seal within the sword was sealed there by the Evil God.