He deflected and evaded the slash, but he did so with the absolute minimum of motion necessary, and that really did set the pattern.

He evaded, he dodged, but he only very rarely did anything particularly... visually appealing or even visually anything much at all. Even when he 'attacked' it was turning deflection into an opportunity, and mostly using Malgus' momentum against him.

The suffocating weight of the dark-side around him certainly affected him. He was expending more effort, working harder, than he might have otherwise been.

He wasn't outwardly doing much but his hair darkened with sweat, but he also didn't fall off balance, become uncentered or sloppy.

He just... did his thing. Was himself. Quietly, undramatically, simply in a very particular kind of zone, doing what he did and fighting as himself.