The Mordenkainen's Sword spell creates a flying sword that acts as a +4 weapon. Those Swords are immune to all physical damage.
|“|| Mordenkainen's Sword|
Upon casting this spell, the wizard brings into being a shimmering, sword-like plane of force that leaps into the wizard's hands. The sword acts as a +4 weapon in all respects and deals 5d4 points of damage upon hitting a target. Once the spell is cast, the sword will float in the air completely under the caster's control. This does not prevent the caster from doing any other actions during the spell's duration.