It was our first session of Curse of Strahd, and I used the Creeping Fog adventure hook to get the party to Barovia. Immediately, they grew suspicious of the mist and cast detect magic.
I was able to reveal that the mist was of a magical nature, but when they pressed me to reveal the school of magic, I had to simply say that it was unclear.
Does anyone know what detect magic would actually reveal?
When they finally reached the Village of Barovia, they came upon Death House and grew suspicious.
One party member was concerned that the children outside, Rose and Thorn, were illusions. They are. She cast detect magic. I had no idea how to deal with this, so I set the DC at 20, figuring Death House cast a pretty good illusion, and in a meta-game sense, I was worried if they discovered the illusion, they wouldn't go through the house, and I'd be stuck. She rolled very low, so I was comfortable and I think they all were, too. But what if she had rolled a 20? At what DC would you set Death House's illusion?
Are there other instances in CoS where I will have similar difficulties, and if so, what should I do?