The initial idea behind the final slash was simple. More energy would transform into more power released during the attack. Noah's law would take care to turn it into a carrier of the many aspects of his existence and create a massive technique that could theoretically stand above everything else.
Yet, that version of the attack was clunky, it required a long preparation, and it would often fail to express the true potential that the accumulated energy could release.
Noah was copying the final slash from a magical beast and was adapting it to his abilities, but he didn't want to leave it as a sheer discharge of power. He was more than that massive armadillo, and his attacks had to show that.
