Dragons?
The atmosphere around them got colder, and colder, to the point where it was physically impossible to survive it for long! Arvena had practically sealed the exit of the nest that they were in, she sealed it with a scorching coating of fire, but that was not enough to make the team comfortable, for a couple of reasons.
First things first, a sealed exit cut down on their oxygen supply pretty quickly, it left them almost breathless after ten minutes of her futile efforts. She had to stop it, because the fireball wasn't even helping the team warm up enough anyway, and that was the second reason why they were not comfortable. The surrounding cold temperature was too much of a competition for her to handle, virtually nothing could battle it!