The air rune is an item used in the Evil Dave's Big Day Out quest. A few are found behind drapes in Evil Dave's Basement of Doom in Doris's house, along with a law rune and earth rune. Dave's spellbook can be investigated to use the runes to teleport the player to the Grand Exchange.
More are given to the player from Clark or Kent in exchange for a flask of stew-water, in order to teleport to the Makeover Mage.
