The conflict of the future is between the absolute who is the God-man, and the absolute which is the man-God; the God Who became man, and the man who makes himself God; brothers in Christ and comrades in Antichrist.
The Antichrist will not be so called; otherwise he would have no followers. He will not wear red tights, nor vomit sulphur, nor carry a trident nor wave an arrowed tail as Mephistopheles in Faust. This masquerade has helped the Devil convince men that he does not exist. When no man recognizes, the more power he exercises. God has defined Himself as “I am Who am,” and the Devil as “I am who am not.”
Nowhere in Sacred Scripture do we find warrant for the popular myth of the Devil as a buffoon who is dressed like the first “red.” Rather is he described as an angel fallen from heaven, as “the Prince of this world,” whose business it is to tell us that there is no other world. His logic is simple: if there is no heaven there is no hell; if there is no hell, then there is no sin; if there is no sin, then there is no judge, and if there is no judgment then evil is good and good is evil. But above all these descriptions, Our Lord tells us that he will be so much like Himself that he would deceive even the elect–and certainly no devil ever seen in picture books could deceive even the elect. How will he come in this new age to win followers to his religion?
The pre-Communist Russian belief is that he will come disguised as the Great Humanitarian; he will talk peace, prosperity and plenty not as means to lead us to God, but as ends in themselves.
He will tempt Christians with the same three temptations with which he tempted Christ. […] The third temptation in which Satan asked Christ to adore him and all the kingdoms of the world would be His, will become the temptation to have a new religion without a Cross, a liturgy without a world to come, a religion to destroy a religion, or a politics which is a religion–one that renders unto Caesar even the things that are God’s.
In the midst of all his seeming love for humanity and his glib talk of freedom and equality, he will have one great secret which he will tell to no one: he will not believe in God. Because his religion will be brotherhood without the fatherhood of God, he will deceive even the elect. He will set up a counterchurch which will be the ape of the Church, because he, the Devil, is the ape of God. It will have all the notes and characteristics of the Church, but in reverse and emptied of its divine content. It will be a mystical body of the Antichrist that will in all externals resemble the mystical body of Christ. […]Then will be verified a pardox—the very objections with which men in the last century rejected the Church will be the reasons why they will now accept the counterchurch.
—from Communism and the Conscience of the West by Venerable Fulton J. Sheen (1948), Ch. 1: The Decline of Historical Liberalism and the Rise of the Antireligious Spirit
For commentary on these passages and the source where I first came across these passages, read Fr. Dwight Longenecker’s blog post Fulton Sheen and the Anti Christ.