Black magic is magic for malevolent purposes, including magic which is demonic in nature (which can only be evil). Faust would be considered a black magician because of the influence of the demon Mephistopheles/Mephisto.
This contrasts of course, with white magic – magic for good purpose and which was usually accompanied with reference to God to underscore the point. While generally magic was demonised by the church, magic was – and is – so pervasive that it can’t really be excised. Some magic has to remain, both for the purposes of the church, in blessings, prayers, and rituals, but also for the people, who daily used talismans, divination, blessings – and yes, curses. What is “luck,” but magic?
So “white” magic could include pagan magic inasmuch as that “superstition” was an integral part of European culture and could hardly be demonised and repressed. Thus the blessing of fields and buildings, which was originally a pagan ritual, was incorporated into Christian practices to satisfy the people and avoid unnecessary confrontation. A cunning man or woman might repeat the same magical rituals as had been practiced into antiquity, but could adapt the ritual of say, collecting herbs, by asking for the blessing of the Virgin Mary.
Traditionally, and in fantasy of course, black magic was performed by witches and warlocks, and the fear of it led to witch hunts and other forms of persecution.
Actual “black” magic depends somewhat on the perspective of the person doing the complaining, but its malevolent nature and intent define it. If a person had a complaint against the village cunning person (shamanic wise man or woman) they might accuse him or her of cursing them. A person could be brought to trial on those complaints with the outcome highly dependent on the use of torture.
In some jurisdictions (such as England which outlawed torture) a charge of witchcraft would likely be dismissed by rational judges in the fifteenth century, but elsewhere many lives were lost to charges of black magic and association with the Devil followed by torture. The very low conviction rates in places which denied torture suggests that both witchcraft and black magic were fantasies of hysterical moral panics. Local grievances could normally be handled otherwise, but torture led to desperate false confessions which led to moral outrage, fear, panic, and more accusations, and more arrests, and more torture, and more panic, and ultimately slaughter.
Where was the black magic and who was the victim? Sometimes “evil” is a matter of perspective, and some times it takes years to see which is which.
Our tendency as a mob to panic and destroy has never gone away, but our carefully engineered social structure and rights and laws protect us. When we are tempted, in a Faustian sense, to dispense with the rules for a supposed higher good; to make an exception by setting aside those rights and laws for just one particular set of unusual circumstances – like “Radical Islam” for example – then we are dismantling the structures which protect against mob panics prior to destroying them.
You want to allow torture to detect terrorists? You’re guaranteed to find whatever you want. Subsequently surprised at how many people can be tortured into admitting they’re terrorist? Better build a wall, though from another perspective it’s really a cage in which you’ve recently repealed your own rights and laws.
The Black Magician
“While the black magician at the time of signing his pact with the elemental demon may be fully convinced that he is strong enough to control indefinitely the powers placed at his disposal, he is speedily undeceived. Before many years elapse he must turn all his energies to the problem of self-preservation.
A world of horrors to which he has attuned himself by his own covetousness looms nearer every day, until he exists upon the edge of a seething maelstrom, expecting momentarily to be sucked down into its turbid depths.
Afraid to die–because he will become the servant of his own demon–the magician commits crime after crime to prolong his wretched earthly existence. Realizing that life is maintained by the aid of a mysterious universal life force which is the common property of all creatures, the black magician often becomes an occult vampire, stealing this energy from others.
According to mediæval superstition, black magicians turned themselves into werewolves and roamed the earth at night, attacking defenseless victims for the life force contained in their blood.”
Secret Teachings of All Ages, p 103. By Manly P. Hall (1928).