Frozen fuel

Exploration Stage: Cozy Mezzanine
From: Icy
Description: The guides complain that their limbs have gone numb from the cold, but oddly enough, the temperature itself is not that low. I don't see any traces of winter magic, but perhaps the guide has been affected by the freezing artifact. Let's look around and see if there are any nearby. Do you see anything frozen?
Completed: Have you found frozen coal? This is the first time I have seen something like this. But this is not an artifact, nor does it emit cold air. The coal is frozen as if a spell had been cast on it, but there is no freezing magic or transformation magic. We do not know what happened.