Ras, The Dancing Blade

Ras, or Ras, The Dancing Blade, is an enchanted longsword +2 which can attack on it's own for 4 rounds. The weapon has a speed factor of 3, weighs 3 lbs and it offers the wearer a THACo bonus of -2 and it deals 1d8 +2 slashing damage. This item appears in Baldur's Gate II: Shadows of Amn and Baldur's Gate II: Enhanced Edition. It's not known where this item can be bought.

In-game description
"Long Sword +2: Ras, The Dancing Blade Beroalf was a barbarian who traveled from the cold north in search of adventure. He sought treasures and glory, but soon all he wanted were companions to share in the excitement of battle, much like those he had left behind in his faraway village. Unfortunately, his coarse remarks and rudimentary hygiene repelled most travelers he met, until he expressed his thoughts to a sympathetic mage. The mage, for a price, constructed Ras, the dancing blade. Though not quite what Beroalf had in mind, he was thrilled nonetheless, and wielded the sword for many years.  How they were ultimately separated is not known."