'Imposters' in the Bible

But evil men and impostors will go on from bad to worse, deceiving and being deceived.

For many deceivers [heretics, posing as Christians] have gone out into the world, those who do not acknowledge and confess the coming of Jesus Christ in the flesh (bodily form). This [person, the kind who does this] is the deceiver and the antichrist [that is, the antagonist of Christ].