The Mask

Mask (pronounced: /ˈmɑːsk/ MASK), the Lord of Shadows, was the god of shadows and thieves in the Faerûnian pantheon. He was a loner god most often associated with thieves or those of otherwise ill-repute. He was a chaotic neutral or neutral evil intermediate deity from the Shadow Keep in the Plane of Shadow, whose portfolio included shadows, thievery and thieves, and previously also included intrigue. Mask's symbol was a black velvet mask tinged with red.
https://forgottenrealms.fandom.com/wiki/Mask