Assassin's Cloak

The Assassin's Cloak allows the player to be less easily detected and increases the chance of a critical hit on an enemy while undetected. It can only be obtained by completing the merchant's quest "An Old Man's Revenge".

Source

 * An Old Man's Revenge (aka Buffbeard's Ring Quest)
 * Merchant

Trivia

 * Although there are various items with the prefix "Assassin's", there is no Assassin's Set.