Cloak of the Thief
|A pitch-black cloak which allows its wearer to excel in the arts of thievery, and can be evoked to release thick clouds of smoke for a hasty escape.|
Being able to generate clouds of smoke and fog on demand is incredibly powerful when used correctly - it allows you to block out all threats not within a 2 tile radius of you, almost like a better version of the Darkness spell, which, while not so useful for ranged characters, is really strong for melee builds and most definitely worth the -2 slaying. Even for ranged characters the ability to block line of sight to a full-screen fire giant or golden dragon makes this cloak useful quite often.
Prior to 0.15, this cloak only penalized damage (-3), not accuracy, and provided a slightly higher stealth bonus.