The most peculiar aspect of Irving's depiction of the devil in the form of Old Scratch is that he is very composed and extremely deliberate.  The devil is not a fanatic or some type of insane force.  He appears in control and very thorough in his dealings with Tom.  By contrast, Tom and his wife are shown to be the most representative form of humanity. They cling to possessions and "the almighty dollar" even more than they do to one another.  Mrs. Walker is shown to want so much in way of wealth that she involves herself in a physical altercation with the devil in a losing confrontation.  Tom Walker is shown to covet so much in way of wealth and possession that he shows myopia towards his decision, something that he regrets later on in his life.  Throughout his coveting of wealth and his equal coveting in escaping his promise to the devil, Old Scratch is methodical and biding his time.  The devil is shown to know the moment as to when he will collect on his debt.  

This becomes one of the most peculiar elements about Irving's depiction of the devil.  He is not peculiar, but rather cautious and very precise in how he obtains Tom's soul.  The most traditional "devil- like" characteristics are given to Tom and not to Old Scratch.  When Irving closes with "Such was the end of Tom Walker and his ill-gotten wealth. Let all griping money-brokers lay this story to heart," it becomes clear that Tom Walker fulfills more of the stereotypical notions of the devil than Old Scratch.  This is the most peculiar thing about the depiction of the devil, almost suggesting that human beings can be more devilish than even the devil could envision.