The Air Sword was a Toa Tool that was regularly utilized by ToaLesovikk to channel his ElementalAir power through. It was once another tool but was altered upon Lesovikk's entry into The Pit.
Lesovikk presumably obtained the weapon upon his transformation into a Toa. He then would have carried it until he entered The Pit and the Mutagen transformed it into the Air Sword. He used the Sword on several occasions until he arrived on Spherus Magna following the Battle of Bara Magna and started searching for Karzahni. The Air Sword was later found in the back of the Tyrant's Corpse, indicating that Lesovikk had might have stabbed Karzahni with it then pushed him into the Iron Canyon.
The Air Sword was released with the Toa Lesovikk in late 2007.