The Devil is beautiful. Let that truth sink in for a minute. I am not exaggerating. The Devil is beautiful. No, he is not beautiful in his wickedness. He is beautiful in how God created him. I know, we usually portray him as a hideous demon to show the gravity of his sinfulness, but that is not the testimony of our faith. The Devil, before he fell into sin, appears to have been one of God's most beautiful creations. That is likely why he fell, in fact. He was so fixated on his own beauty that when God created Mankind and said they they would be the pinnacle of creation, the Devil could not handle having someone more beautiful than he was, so he rebelled. There is nothing that says that he became ugly in himself. Yes, his sin has made him to be ugly, but that is not what he is like by nature.
Why do I bother mentioning this? It is not merely an academic fact. I point out that the Devil is beautiful (still) because he never shows his true sinful self. He always tries to portray his original beauty so that we never recognize how horrid sin is; even Satan worshipers have no idea of his evil. Whenever someone says "that sin is not all that bad" or "the Church is too harsh about that sin" or even, "the Church is wrong on that moral rule", they have fallen into the temptation of the Devil and are seeing sin the way he sees it: disguised as something pleasant and good for them.
So when the Devil comes to tempt, he only shows his "best side". He appears nice, pleasant, and congenial. He coerces us into thinking sin is as beautiful as he was in his original nature. He makes himself out to be an angel of light, rather than a devil of corruption. Would you recognize him for what he is? Can you see the Devil (and the temptation that he gives you), not just in his original purity, but also in his current fallenness? Can you see past the Devil's lies and see sin for what it really is? It may be hard to do, but it is crucial if we are going to resist his attacks.