My family has a huge number of black magicians. The spells do work, but they backfire also. They should be a big NO NO because they'll ruin your lives. Honestly speaking, they arent truly hocus focus magic, but guidance from Jinn and universal laws. Allah already said that those who do good will receive positive rewards and those who do bad will receive negative rewards. Allah is all about fairness in objective way.
Jinns should never be trusted..esp the satanic ones. They are cold blooded dumb, but aggressive snakes. They don't like us because we have taken up their lands and they tend to think we are inferior. If you want to be a satan worshiper you will be bullied like crazy by them. Examples:
They'll tell you to sacrifice something to them (it may mean killing even a human)
They'll make you eat the dirtiest things
They'll tell you to not bath for days
They'll tell you to do everything abnormal and sinful
Universal law works differently. Its about wishing or praying to see someone in bad condition. In normal English, it is called curse. Any ordinary human can do it. Black magicians recognize it as black magic because it is meant to do harm. Sadly, in Islam, curse is not seen as bad, but trust me, it does backfire in the form of monetary loss, poverty and harm towards a loved one.