"The Angel of Light"
One of the things that's most often overlooked about the nature of Satan is his metamorphic character. When we speak of metamorphosis, we speak of that which changes in its outward appearance. For instance, the crawling caterpillar goes through a metamorphosis to become a beautiful butterfly. What I mean in describing Satan as metamorphic is his capacity, as we say in theology, to manifest himself subspecies boni, which literally means "under the auspices of the good"--that far from being the ludicrous character in a red suit and carrying a pitchfork that we talked about in the last chapter, he rather has the capacity to manifest himself as Scripture says, as an angel of light (2 Cor. 11:14). He doesn't come against us baring fangs, with a hideous visage; rather, he approaches us disguised in beauty, looking attractive. That's part of the allure of his seductive techniques. If Satan were to manifest himself in a human person, it would not be some horrible, famous, miserably wicked person like Osama bin Laden or Adolf Hitler. Rather, he would come on the stage of history looking like a saint. Satan would try to appear as someone laudable, someone who manifests some kind of righteousness, but of course, he would do it in a hypocritical manner because he is a liar.
Excerpted from Unseen Realities: Heaven, Hell, Angels and Demons by R.C. Sproul (Christian Focus, 2011). A PDF sample of the table of contents and the preface are available here: LINK.