User blog comment:Crimson and Darkness/Volume 25 discussion blog/@comment-121.121.95.140-20180405034821/@comment-86.149.140.107-20180406035352

Their sacred gears have opposite powers but Vali powers those modes diffrently even Ophis said that the blessing she used on him is not the same as Issei's. One of the reasons their have mirrored each other is like Albion learnt to counter Ddraig Vali learns to counter Issei. So when Issei powers level up he uses hes vast Devil power and magical knowledge to force his Divine Dividing to come up with a counter to it.