This DRIZZT.ITM weapon is used by Drizzt Do'Urden in the Baldur's Gate II: Shadows of Amn and Enhanced Edition as his only melee option, held in the quick weapon slot.
Drizzt does not dual wield Twinkle and Icingdeath as his animation sprite shows. He is actually armed with just this single item.
The weapon is a +5 enchanted item classified as a Large Sword and provides both the +5 bonus to THAC0 and Slashing damage. The weapon has a Speed Factor and range of 1.
If Drizzt's strength is boosted (for example by using his Potion of Stone Giant Strength), then the weapon will benefit from that and apply the extra strength damage on each blow.
Any successful hit has a 30% probability of adding +30 slashing damage to the target, however a Saving throw vs. Death with a +4 bonus will negate this.