As soon as the evil cleric begins casting Nestor locks his eyes on the man.

"Celaria, do what you can to bring us light!" Nestor says when the darkness covers them.

Moving directly for the place that he last saw the cleric, Nestor tries to grapple with him while saying, "I am trying to grapple with the evil one!"
I have no other love, no greater desire, than to be wholly given to the Commander's service, but man's heart is too easily corrupted and his mind too quickly weakened to hold faith in my own heart and mind. I believe that it is far wiser to trust only in the Invincible.