Witchcraft, and all related "arts", are absolutely forbidden by God in Scripture.
Divination (the attempt to foretell the future or discover hidden knowledge by occult means), omen-interpretation, fortune-telling, sorcery of any kind, mediums, necromancy -- all was forbidden by God (Deuteronomy 18:10). Techniques often used in these practices are the Ouija board and Tarot cards. All these practices are detestable in God's eyes. It was for all these practices that God sent in the Hebrews to destroy and drive out the Canaanites from Palestine.
The New Testament condemns sorcery as a manifestation of evil (Galatians 5:20). Witchcraft is a sure way of bringing God's fiery wrath down on yourself (2 Chronicles 33:6). There is no such thing as white witchcraft; in God's holy eyes, all witchcraft is black.
Why is God so hostile to witchcraft? It is because witchcraft is all about knowledge and power, divorced from God. It is an attempt to gain supernatural power over the world for one's self or others, apart from God. The diviner seeks to know the future, apart from God. The reader of omens seeks hidden knowledge, apart from God. The witch seeks to exercise power, in defiance of God. The whole enterprise is fueled by lust for worldly things, and unbelief.
God wants us to rely on Him by faith alone in His Word, while witchcraft pretends to offer power apart from reliance on God. God says to deny wealth, power, fame, pleasure, influence, or worldly success in favor of serving Jesus Christ, while witchcraft pretends to show a path to all these things. God says to worship Him alone, while witchcraft always leads into idol-worship. God says we should bow to His supernatural sovereignty, but witchcraft pretends to offer us our own sovereignty by other means.
Another reason God hates witchcraft is because demons are the unseen power behind mediumistic practices (setting aside ordinary fraud for the moment). There are only two spiritual powers in the universe -- God and Satan. God is good always, Satan is evil always. Nature has no hidden paranormal powers waiting to be tapped by ritual -- nature is subject to God. There is no power battery in-between God and Satan, waiting to be tapped. If you aren't going to God, then you're appealing to Satan, even if that isn't your intent.
The spirits of the righteous dead go to heaven, while the spirits of the sinful dead go to hell. This means the spirits contacted through mediumistic practices are evil spirits -- demons. And demons only lie, steal, kill, and destroy. People who engage in divination practices open themselves up to demon possession (example, Acts 16:16). This is why God vowed a death-sentence against anyone in the Jewish nation who engaged in witchcraft (Exodus 22:18, Leviticus 19:31). This was a way of protecting the rest of society from a social cancer.
Some popular depictions of magical things are just silly. "Ghosts" chase Pac-Man through a maze, Dr. Strange jumps through sparking portals -- these are just foolish, an, more importantly, they are impossible to replicate in the real world. More serious are depictions of real things, like seances, or water-witching / dowsing, which (unlike flying carpets or Sabrina making things disappear) are ceremonies that can actually be performed by real people. Casper the Friendly Ghost is one thing, actually showing people a ceremony on how to allegedly contact the dead is another.
(Some people point to the story of Samuel's spirit rising from the underworld, in 1st samuel 28:3-25, as an example of a "positive" appearance of the spirit of the righteous dead. The problem with this attempt to sanitize necromancy is that Samuel's spirit pronounces doom upon Saul (I take the view that it actually was Samuel, since he chastises Saul, his words honors the Lord, and his prophecy of Saul's destruction at the hands of the Philistines came true). This story should be taken as a freak occurrence, and it certainly doesn't endorse divination; rather, it condemns it by condemning Saul to death.)
Have nothing to do with real witchcraft.
A cult is a religious organization that says it's Christian but denies one or more of the fundamental truths of Christianity. These would include monotheism, the Trinity, the inspired reliability of the Bible, Christ's deity and humanity, or salvation by faith. They are usually dominated by one overbearing, dictator-type leader, use abusive forms of authority, and exploit the members financially and often sexually.
A sect is a Christian group that is basically sound in its preaching and teaching, but has elevated some secondary doctrine, peculiar tradition, or unique practice up to such a level of importance that the group breaks fellowship with other believers. Examples of this could include foot-washing, modes of baptism, or opinions about the time of the Rapture.
Cults are not Christian at all, even though they claim to be. For example, the Church of the Latter-Day Saints (Mormon) is not a Christian organization. Sects are Christian but they're divisive over secondary issues.
For example, the Missouri Synod Lutheran Church forbids its members to take Communion with any church but another Missouri Synod Lutheran church. If a Missouri Synod Lutheran was to break bread with us at our church, he or she would be excommunicated by the Missouri Synod. The Lutheran policy seems to say that no other Christian churches are "real" Christian churches, but that we're all heretics. This is the sin of sectarianism. Paul talks about this in 1st Corinthians 1.
Both of these are bad, though cults are worse because they actually deny the faith, where sects unbalance the faith. However, a spirit of denominational superiority, church-splitting, and judging one another over matters of personal conviction, weakens the Body of Christ and makes us more vulnerable to Satan's attacks.
There is a very old Christian doctrinal term, which is hard to understand and needs some up-dating: impassibility. Have you ever heard it? I only began interacting with it a couple of years ago. It's important, because it's about God.