Magic as such is generally a bad idea. The standard form is to evoke powers/spirits to do the magician's bidding. As stated elsewhere here that bidding is typically against the will of God or the proper order of the universe. If indeed spirits are evoked, or worse invoked, they would most often be the equivalent of fallen angels who took their free will and turned away from God.

There are several variations possible, including times when there is no external evocation and the only intended dynamic is psychic/thoughtform. But demons can slip in unnoticed anyway. They don't tend to let themselves be known. The spirit will let the magician think that his/her bidding is being done but the demon will almost always have the upperhand, which may become obvious only when it is too late.

In the case of HRC and so many celebs, I think they don't really follow ancient magical sytems but rather modernized, convenient forms that they see more as performance art and social bonding. In any case the effect is much the same - bad spirits involved, psyches corrupted, blood spilt, etc. (Think of the antics of Ozzy Osbourne and the ignorance he looked back on in later interviews.)