I always assumed lust of the flesh was the essence of the devil.
Thanks for your input. I would submit to you that the common denominator between the devil and mankind is sin. The problem with sin is that it breeds within an individual a strong desire for ungodly pleasure, which then results in corruption of that person's character. The desire builds as we partially satisfy its hunger, and then leads to blazing lust (James 1:15). The devil is a devastating example of the deep and long-term progression of sin's effects, but sin and the devil are two separate things. The devil is a rebellious spiritual being who wants to see sin have its way with mankind, that we might be consumed with lust for anything but God.
I might classify the devil's essence with verses like 1 Peter 5:8 (one who devours) or Revelation 12:9 , 2 Corinthians 11:3 (one who is crafty or deceives) , etc.
The lust of the flesh, I would say, (you should do your own study!) relates more to the course of sin. The devil's character/essence is completely lustful, I am sure, but its because of the sin in him.
Flee youthful lusts! Don't let sin do its work in your heart. We should pray without ceasing for God to keep us pure!
Hope that helps?
FYE: For Your Encouragement