Affecting His Spirits
As many techniques fell together, different attacks landed. Before the techniques would release their full might, William would flash, pass through them, and weirdly enough he'd look like he was absorbing the techniques, adding them to one of his tails!
He wasn't truly absorbing it, but using an element that was used in these techniques. As he didn't have all the elements other masters had, he had to improvise and mix a few elements together, making different element masters release their techniques in the same spot.
And in the middle of these techniques combining their full devastation force, he'd flash, and use an element present in that mix, while activating another Holy Sword technique. Doing this would let the explosive techniques that were in the middle of getting unleashed merge with his Holy Sword, using that common element as a medium, ending up forming a layer over one of his tails.