Comments of chapter undefined of Vengeance of the Fallen Magus

Short Explaination: Aura = Element that only specific race could master, in exchange, the person who had this element couldnt be able to learn any element (except Rune), unless they maanged to acquire one of the mythical weapon, Notable Owner: Chris Jansen (Innate), Asta (Innate quad with his Earth, Sound and Space since he is the god's descendant), and Elanor (Innate since he is half-elf)

How is "rune" an element

there is 2 wind the 3rd and the 11th from