The void nemesis starts of his attack with the spiralling arms. However, outside of range of those void arms, he also spawns a swirly orb that at the same pace circles around. That swirly or w/e you want to call it can become invisible if the nemesis himself is outside of your screen, as just happened to me in a cemetery.
On a sidenote: he also feels quite severely overtuned compared to all other nemesis types.