It was a commonly known point that an undead was weak during the daytime. In fact, the undead emit a black aura when they are in the sun. It’s something like HP, which one could see. However, it was released into the air with time. Perhaps that was the real nature of the haze, a grand version of the aura that breaks out during the daytime.
“Hmm, I wonder if the lost magic power is being restored now?”
“I guess so. Well, that has nothing to do with us now.”