Protestantism

2 Thess 2 says the Antichrist will show up prior to the Second Coming of Christ. Revelation 14. 6-11 says 3 angels from Heaven will show up sooner or later. Daniel 12. 1 says the archangel Michael will show up, eventually, to deliver the Jews. But watch out for angels from Hell. 2 Corinthians 11. 13-15 says Satan masquerades as an angel of light. 1 Peter 5. 8 tells us to be sober and vigil because the Devil walks about like a roaring lion looking to devour those whom he may.

2 Thess 2 also says, in so many words, that the Antichrist will sit in the Holy place.  The standard interpretation is that the Jewish Temple in Jerusalem will need to be rebuilt for the prophesy of 2 Thess 2 to be fulfilled.  But this Temple would not be considered Holy by Christians, as St. Paul has already told us that the heart of a Christian is the temple of God.  Jerusalem is still considered Holy by Christians, so perhaps if the Antichrist goes to Jerusalem the prophesy of 2 Thess 2 would be fulfilled. And if the Antichrist writes satanic heresy on the hearts of Christians, that is, on the hearts of Christians who have fallen away but who are destined to repent and go to Heaven, then the Antichrist might be said to be sitting in the Holy place.

If an angel shows up, and if he tells Roman Catholics that the Roman Catholic Church has been dragging people down to eternal perdition for centuries, because Rome is a false church, because Rome is lost in heresy, then the Catholics will say that angel is an angel from Hell. But Protestants will say that angel might well very well be an angel from Heaven.

If an angel shows up and if he tells the members of the ELCA - the Evangelical Lutheran Church in America - that the ELCA is a false church which drags people down to perdition, then the members of the ELCA will tend to see that angel as an angel from Hell. But if he is an angel from Heaven...

Why do churches become false churches? They violate Galatians 1. 8-12, John 14. 23-26, 2 Thess 1. 8, Revelation 21. 8, 1 Corinthians 11. 27-29, Revelation 22. 17-19...

Churches become false churches when they celebrate Holy Communion in an unworthy manner. 1 Corinthians 11. 27-29 says you drink damnation into your soul if you do that. The ELCA gives the bread and the wine to pro-choicers, to pro-gay marriage people...