Looks like most people have give adequate answers already and the OP has most likely left.
But others may be reading this thread who may have a similar outlook or question.
I think it's important, not only to know the commands of Christ, as outlined in scripture (which directly and unambiguously forbid pagan practices, such as wicca, witchcraft, fortune telling, etc), but knowing "why" is important.
None of God's commands are arbitrary, but have purpose.
To the uninitiated, these things seem like arbitrary limitations, because they have no knowledge of the "Christian/Biblical paradigm".
To pagans and other religious groups, many believe it permissible to mix and match faith, religion, mysticism, etc, and this was common in the ancient world too, you had many polytheists and so on.
However, from a Christian point of view, there are only "two sources of power" in the universe, God, or Satan.
Anything that is "magical", "spiritual", or provides some kind of "immaterial power", or "supernaturalism" either has to be divine, or... not divine. The divine power, being from God through means of his Holy Spirit (that in itself being another topic, as there are different views of just what the "spirit" is, but I digress), whilst the alternative would be getting power from the Devil (or the demons who work with him).
There is no "middle ground" or "neutral source of power" in the scriptural view. It's either coming from a holy source, or from elsewhere. If God has not authorised it, or granted it, then the power is coming from somewhere Satanic.
This is why these practices are forbidden scripturally, because it's not just "calling upon some power" that's in the universe, but rather, it is attaching one's self to evil forces. When we are in Christ, God's spirit is within us, and it "seals us" in the promised salvation, but we can "grieve it" with unholy conduct.
If we practice things which are Satanic in nature (again, this is the Christian paradigm), then we are having that "evil power" or spirit come upon us and within us, and that invokes death and destruction. And is it something which God finds foul. His Spirit and the spirit of evil cannot coincide.
As scripture says "you cannot sit at the table of the Lord and the table of Demons".
It is both a matter of God's sovereignty, as well as a matter of real spiritual forces in conflict of one another.
It may seem very "black and white", but the Bible's view of supernatural/spiritual forces in itself, is a black and white paradigm. Therefore, one cannot be Christian, whilst calling upon the powers of what Christian scripture would define by nature as the powers of Satan.
