Frozen prankster

Exploration Stage: Artifact Bank
From: Kira Woodville
Description: We need to plug the security hole in the bank that the hobgoblins used to break in and get rid of the culprits. Why does an energy meter emit a rattling <warning tone> near an artifact that looks like an old-fashioned foot warmer? Bring it here so we can look into it.
Completed: Thank you for delivering the foot warmer, it doesn't have an ID on it. It does not appear to be from the bank. Did the hobgoblin bring them? There is ice inside. It is not due to air conditioning as it is always cold here. How did the hobgoblin use this to break into the bank? I don't understand it at all.