Chaos Blade

Chaos Blade is an enchanted short sword +2 which can only be wielded by Tieflings, which means that only Haer'Dalis can wield it. It inflicts 1d6 +2 points of piercing damage, has -2 THACO bonus, a speed factor of 0 and it weighs 1 lbs. The opponent also loses two points of Dexterity for 30 seconds when hit by the weapon. The dexterity penalty shoudl make it easier to hit the target to hit, but it's not known if the penalty stacks. This item appears in Baldur's Gate II: Shadows of Amn and Baldur's Gate II: Enhanced Edition.

Haer'Dalis has this weapon equipped when he joins the party in Shadows of Amn and Throne of Bhaal.

In-game description
"Chaos Blade Chaos is a +2 short-sword usable only by tieflings. Everytime it strikes an opponent, he or she loses 2 points of dexterity (for 30 seconds). Haer'Dalis prefers using Chaos with its partner -- Entropy. When dual wielding these two blades, Haer'Dalis is a dangerous opponent."