A few quick points Kabar fashioned his armor from the many vex remains. Which implies the armor set is big. He used his light to make the shield, and the vex consumed his brain and blood. So to me this implies atheon is the vex armor with the body of Kabar while his soul is the sheild. So this means the wound he put on the vault is himself. He became the light and the dark, ying and yang. So atheon (kabar). Can't destroy the sheild because it is a part of himself. Which is why he sends it through time, because it has to exist for him to live. so the only option to get it as far away as possible. (But we can use it to destroy him). So in closeing, when you destroy atheon you also destroy the sheild. Brainstorm done.........