Well, a common belief about who the first beast is is that it’s Rome, specifically the Papacy. The Papacy is not mentioned by name in the Bible, not the exact identity of the beast mentioned either. Therefore it does require wisdom and understanding to figure out who the beast is. There are many theories and all of the theories refer to non-Biblical figures such as Nero, the Papacy, or Islam just to name a few examples.
Islam does have a branch on eschatology, too, and it’s essentially the reverse of Christian eschatology. I’ll try to explain now.
Is Islam, before the “day of judgement” or “day of the Lord” in Christianity, an Islamic man will appear during a time of tribulation and rule the world for 7 years. This man is know in Islamic eschatology as the “Mahdi.”
As I said, Islamic eschatology is like a reverse of Christian eschatology. In Christian eschatology, the one who will rule the world is the beast, also known as the anti-Christ. Those who don’t submit to the anti-Christ will be beheaded per Revelation 20:4. As you correctly pointed out, beheadings fit the Islamic ticket.
Islam also believes in Jesus Christ. They don’t believe in Jesus Christ the same way Christians do. They believe after the “day of judgement” that Jesus will return and destroy Christianity. Islamic eschatology is a reverse of Christianity. In Islam the good guy comes followed by another good guy. In Christianity a bad guy comes first followed by Jesus the good guy.
The second beast is the false prophet per Revelation 13:11 “he had two horns like a lamb, and he spake as a dragon.” This is the one who comes after the first beast, aka anti-Christ and is known as the false prophet or in Islam Isa Son of Maryam.
Another piece of supplemental information is the “bismillah” and “666” in Greek. The bismillah is an Islamic symbol and 666 is the number of the beast. Imho, I don’t think that’s a coincidence, but rather a prophetic clue. I’ll post a picture of the bismillah next to 666 in Greek below.
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In conclusion, first beast is an Islamic Mahdi.
Second beast is Isa Son of Maryam.
Mark/number of the beast will be the bismillah written on their forehead, typically worn as a bandanna by some Islamic sects, which looks like 666 in Greek.
So it’s my belief that by the time all of this transpires, Islam will have swelled its numbers dramatically compared to Christianity and will have conquered the world. True Christians will die for their fair on before ever denying Christ and Jesus will return after the great-tribulation to essentially save the world, destroy all enemies of the cross, and setup His millennial kingdom.