The Xarrnous's Second Sword Arm, also known as Gauntlets of Weapon Skill, are a pair of gauntlets made to increase the chances of hitting enemies successfully. They offer a bonus of +1 to THAC0. The Gauntlets of Weapon Expertise will do this as well, but they also offer a +2 bonus to damage.
Gauntlets of weapon skill: 'Xarrnous' Second Sword Arm'. Perhaps the most well known owner of these gauntlets was a mercenary, named Xarrnous. He specialized in smuggling, and frequently loaned these gauntlets to clients if they were to travel with him. In his eyes, an extra sword arm was always handy.