"But Elymas the magician (for so his name is translated) was opposing them, seeking to turn the proconsul away from the faith. But Saul, who was also known as Paul, filled with the Holy Spirit, fixed his gaze on him, and said, 'You who are full of all deceit and fraud, you son of the devil, you enemy of all righteousness, will you not cease to make crooked the straight ways of the Lord?'"
— Acts 13:8-10 (NASB)
It is important to note that in verse 6, this self-proclaimed "magician" is first identified as "a Jewish false prophet". It seems that most if not all false prophets come in the character of Jannes and Jambres, Pharaoh's court magicians who, to a point, imitated Moses and Aaron the true prophets of God. Here we are provided with the ultimate goal of false prophets, to turn others "away from the faith". Just like a magician who uses misdirection to redirect the audience's attention from what they are really doing, false prophets are intent on getting believers to look away from the true faith toward a counterfeit one.
It may not be apparent to the majority at first glance, but eventually it always comes out where false prophets are concerned. Ultimately their basic character which is "full of all deceit and fraud" comes to light. But in the mean time, their inward character which can remain disguised for a time is actually betrayed by their teaching. Paul reveals the way he knows is dealing with a false prophet by stating, "Will you not cease to make crooked the straight ways of the Lord?" Like Pharaoh's magicians a false prophet might effect some impressive signs and wonders, but they are always betrayed by their false teaching. A miracle, however real it might be, never brings with it the authority to override the Word of God.
Notice Paul does not accuse the false prophet of "replacing" the "ways of the Lord" but making them "crooked". They know they do not need to invent something new but only need to successfully twist, corrupt, or dilute what has already been established. An obvious one which I have seen many of our present day contemporary false prophets do which immediately betrays them is how they twist portions of Scripture to make the listeners feel good about themselves instead of being convicted by sin and driven to repentance. It is not that those who immediately identify false prophets are so much smarter than everyone else, they just happen to be the ones who steadfastly remain in God's Word so that attempts to make it "crooked" are readily apparent.
Ultimately the false prophet is the "enemy of all righteousness". Their ultimate goal is to foster unfaithfulness by what begins as subtle corruption of God's Word and ways, eventually leading further and further away. We should not be surprised when we encounter the followers of such who although still claiming to be "Christian" are in fact so far from it that they take positions completely contrary to those of a true, Bible-believing Christian. It is not the faith in the false prophet's miracles or prophecies as to whether they are real or not — that is the magician's gift of misdirection; it is buying into the accompanying twisted message leading from true faith to faithlessness. †††