The rapier will fight by itself as long as Widseth is within 30′. Physical barriers do not sever the mental connection between the rapier and its owner. It can’t chase and fight flying creatures, but it can be extended (within the 30′ range) to fight a foe separated by a chasm or physical barriers. While the sword fights, Widseth may do whatever he likes, including attack with another weapon, cast spells, or perform bardsong.