The first time he flees, Caztor tries to bite, moves west, then tries to bite again. Then we hear Veriak yell about being attacked by the nightwalker, then he runs back into the room with Caztor (presumably fleeing from the Nightwalker) and gets bitten again.

I wonder whether the nightwalker attacking was instant or if Veriak would have had time to gentlewalk after the shadowdisappear.