A staff meeting to introduce new employees would be an appropriate setting to use jargon. Jargon is language familiar to a certain profession and so in this case it will allow the new employee to recognize the jargon.
Answer: Characters don’t necessarily have to be immortal to be evil, though some gods tends to be evil with their powers and put it to bad use. As for mortals, they’re actually likely to be less evil as they’re actually humans.