"You see Hell, where the souls of poor sinners go. To save them God wishes to establish in the world the devotion to my Immaculate Heart. If they do what I will tell you, many souls will be saved, and there will be peace... But if they do not stop offending God... He is going to punish the world for its crimes by means of war, of hunger, and of persecution of the Church and of the Holy Father."
II Peter 2:1-3:
But there were also false prophets among the people, even as there will be false teachers among you, who will secretly bring in destructive [damnable, KJV] heresies, even denying the Lord who bought them, and bring on themselves swift destruction. And many will follow their destructive ways, because of whom the way of truth will be blasphemed. By covetousness they will exploit you with deceptive words; for a long time their judgment has not been idle, and their destruction does not slumber.
The Devil’s attempts to deceive through false teaching have never stopped. Jesus warned in Mark 13:22 that, as we approach the end, it will be especially intensive; “For false christs and false prophets will rise and show signs and wonders to deceive, if possible, even the elect.” He warns that, if it is possible for us to be deceived, we will be deceived by false doctrines.
The source of false doctrine is demonic. Paul writes in I Timothy 4:1-2:
Now the Spirit expressly says that in latter times some will depart from the faith, giving heed to deceiving spirits and doctrines of demons, speaking lies in hypocrisy, having their own conscience seared with a hot iron.
Paul is writing of men who listen to, consider, follow and then teach doctrines twisted from their biblical base (II Peter 3:16).
He adds in II Corinthians 11:13-15 that, though the false doctrine comes through a man, the real source is Satan. The man is just a servant:
For such are false apostles, deceitful workers, transforming themselves into apostles of Christ. And no wonder! For Satan himself transforms himself into an angel of light. Therefore it is no great thing if his ministers also transform themselves into ministers of righteousness, whose end will be according to their works.”