Codex is correct and let me give you an example of a time the "love magic" backfired.
A young woman wanted to get a guy she wanted to "own" to forget his wife and love her alone.
At the time, he was my teacher; we were very close friends.
It did work to get rid of his wife; but he then fell in love with ME~ maybe b/c I was close by and he already had feelings of affection for me. However, since the young woman was successful in getting rid of the wife, she then managed to move in w/him; the lust part apparently worked.
After a while, however he tired of her and though she was a minor and made his life hell (if you get rid of me, I will tell the police who will put you in jail) and wasn't interested.
Meanwhile, she did it again. Again, he went crazy for me, still a student of his. it also worked on me as well, and I was crazy for him.
Later, after some painful time of my husband getting angry, and me pulling away, he let her this time -- the spell was one that was to make him forget me. It only made him extremely ill for the past 18 months. He is actually showing signs of schizophrenia. The young woman got tired of this and moved out...about 4 months ago now. In the past month he is getting more and more clear-eyed. Though he and I still enjoy a very close friendship it isn't crazy anymore as it was before.
Hope this helps. in conclusion, I strongly urge you NOT to engage in black magic. Even if it works it has side effects that have high cost and it doesn't last all that long, typically.