Shar reaped the rewards of Mystra's death and created Shadowfell
After Shar created the Shadowfell, She abandoned the Tower of Loss and created a new realm in the Astral Sea, larger than any of the others there. Among the dark scenery, with its black sand and shadowy natural features, lay the Towers of Night. Her new abode, a more palatial one than her old home, was built atop the tallest mountain of this realm. Access to the Shadowfell was easy from here and she shared the realm with Talona, Sseth, and Zehir.
On this day the Towers of Night would be visited by one of Shar's worshippers who had committed a crime so detestable, it made her recoil from the individual. It was then Shar deemed the man unworthy to walk the Astral Plane. A punishment fitting to the crime would be hard to find, but she came up with an idea. She enlisted one of her devout followers, Klorr to design a device orchestrating the imprisonment that would benefit the ones she would deem “worthy”.