"He required everyone—small and great, rich and poor, free and slave—to be given a mark on the right hand or on the forehead. And no one could buy or sell anything without that mark, which was either the name of the beast or the number representing his name. Wisdom is needed here. Let the one with understanding solve the meaning of the number of the beast, for it is the number of a man. His number is 666." (Revelation 13:16-18)
The Antichrist (the beast) will be helped by Satan (the dragon) another person called the false prophet.
"And I saw three evil spirits that looked like frogs leap from the mouths of the dragon, the beast, and the false prophet. They are demonic spirits who work miracles and go out to all the rulers of the world to gather them for battle against the Lord on that great judgment day of God the Almighty." (Revelation 16:13-14)
If we are in the era of the return of Jesus we should examine what is taught us by religious leaders. The only way to identify false teaching is to know what the Bible teaches by reading it for ourselves.
"For such men are false apostles, deceitful workers, masquerading as apostles of Christ. And no wonder, for Satan himself masquerades as an angel of light. It is not surprising, then, if his servants masquerade as servants of righteousness." (2 Corinthians 11:13-14)
It is a sobering thought to realize that there are religious leaders who are actually servants of Satan. Jesus Himself warned His disciples that in the era He returns "many" Christians would be acknowledging Jesus as the Christ but would be deceivers.
"While Jesus was sitting on the Mount of Olives, the disciples came to Him privately. “Tell us,” they said, “when will these things happen, and what will be the sign of Your coming and of the end of the age?” Jesus answered, “See to it that no one deceives you. For many will come in My name saying I am the Christ, and will deceive many."
Note again, Jesus said the sign of His coming would be that "many" who are saying Jesus is the Christ will be deceivers. Not a few, but MANY!
Christianity today is divided into countless sects, each claiming they are teaching the truth about Christ. How can we distinguish the deceivers? The only way I know of is to prayerfully read the Bible for ourselves.