A Number Two who is the Number One's voice of reason. Their advice is valuable to the boss because they're usually right, which puts them in a unique position to "Speak Truth to Power" when other staff might be scared to contradict the boss. This kind of job security is largely self-reinforcing - the boss won't fire him because he needs his uniquely honest advice, but he only has the freedom to be honest because he knows the boss won't fire him. Often the smartest guy in the room, or just a calming influence to a Hot-Blooded boss. There's a high likelihood of his being a retained lawyer.