Damien saw it from the ground.
Once he managed to clear the majority of the infectious fog in the air, he was able to perceive it much more clearly, and despite seeing Iris' condition become worse and worse, he wasn't able to move instantly.
He had to first get rid of the plague abscesses on the ground, a task he'd almost finished at this point.
The Plague Lord couldn't control them anymore, so he didn't face as much resistance as he worked. And with his layers being mostly stripped away, Damien's workload stopped increasing as well.
He eventually finished, and when he returned his attention to the battle, he saw that situation.
Iris and the Plague Lord were standing several tens of millions of kilometers away from him, but his vision had improved during his stay in the Ancient Battlefield, allowing him to see them.
This situation was at a standstill.
But this kind of standstill was disadvantageous in every way.
