Mercykiller Ring

Mercykiller Ring is a ring which offers +20% to move silenty, hide in shadows and set traps. The ring can only be worn by Thieves. This item appears in Baldur's Gate II: Shadows of Amn and Baldur's Gate II: Enhanced Edition. It can be bought in the Adventurer's Mart, by the woman in the middle of the store.

In-game description
"Mercykiller Ring The Mercykillers are a powerful faction based out of the planar city of Sigil. This ring is given out to Mercykiller assassins when they are sent out to punish those who have broken the laws of Sigil. Often these assassins will roam as far as the Prime Material plane."