The Heavenly Sin Divine Sword 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 whereabout's 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 it, in exchange for world dominance. 
Over half a year since defeating Xuanyuan Wentian and the Devil Spirit within was dead, Yun Che had constantly been smashing the Heavenly Sin Divine Sword with the Heaven Smiting Devil Slayer Sword during this entire period and it had yet to receive any scars. A dead sword without a spirit with its power completely depleted was still unable to be destroyed by the Heaven Smiting Devil Slayer Sword. The Heavenly Sin Divine Sword was a genuine primordial devil sword. Just the quality of its material alone was something incomprehensible by those in the Profound Sky Continent. In the end, it was eaten by Hong'er.
It's true name is Eternal Night Devil Sword.
- The Devil Spirit within the sword was sealed there by the Moon Slaughter Devil Sovereign.
- The Devil Spirit sealed within the sword was the soul of the son of the Moon Slaughter Devil Sovereign.