The darkness that bordered the tiled space was made using the extreme properties of [Evil Darkness] that Skullius could access, defining the element as he pleased. He was that in tune with it, as he was with [Just Light].
There was no greater inescapable mass, an impossibly thick boundary, like darkness. It made the perfect barrier against attacks of most kinds. The great void which covered the entire Reality was a prime example of what darkness could accomplish.
But as powerful as the barrier was, Skullius could have made it better if he didn't fear losing more Amras needlessly. That was the greatest weakness he had while in the First Phase of the War Body. His Amras reserves were the same as those he had while assuming his Default Body (without the augments from something like [Justified Maximum). His Amras well couldn't handle the strain from the high-powered abilities he had to access to now. For that, he had to wait until the five-minute timer was done.