Dark magick brings power, but power does not bring one's true desires nor does it bring happiness. Even if it does bring happiness it is always short-lived and you must hurt more than you had originally because of this new loss. But then, all things are taken and granted eventually so where is the problem with the dark arts of magick? The problem is that it feeds on the life of the living: human blood, animal blood, people being killed for your own selfish or sometimes not so selfish desires-- yet there are those that continue to practice it. Most ask why this is, the answer is as plain as the nights are star-filled. "Power and the thrill the darker side of nature brings us is well worth the risk of losing all that you have known," or so these practitioners may try to argue. Nothing is truly pure as nothing is truly evil. There can never be a fully pure or fully evil power in the world, but the means in which power can be used can often be perceived in such a way.
While there may not be any true "evil" nor any true "pure" way to live there is still right and wrong. Good and bad. Just and unjust. Righteous and cruel. Whatever you would life to call these things. Though most do not see it every human being makes pure and evil decisions everyday. Even if it is something that seems little at the time it will come back to you down the road. Say, for instance, that you wake up in the morning and do not attend a class you know you should be going to. Now, when an examination comes around or a quiz over the material from that day you will not know it (under these theoretical conditions alone without outside involvement or anything added into the mix) and would most likely fail said exam and/or quiz. On the flip side of such an act if you do go to class you will (again theoretically) pass the examination or quiz.
This same concept can be applied to almost anything. Though most might not take the time to do so it can be done. Things are not as they always seem. There is often trickery and underlying causes, effects, and consequences to actions taken and even those that are not taken. To truly see what is right or wrong in your own eyes you must look beyond the surface. Do not fear what you will find though it might be the most horrible truth imaginable. This is true, you could find out a horrible truth, but you could also find a truth so right that nothing can change that or take it away.
So I end with this, do not take anything for granted and do not justify an act as good or evil. The world is not black and white nor are the problems that it may throw your way or actions that people take. There are so many shades of gray in-between "black" and "white" that it will always make mankind wonder if there truly is "good" and "evil". The true nature of things has never been that simple, nor will it ever be.