While the important of belief has been raised several times before, it is important making special mention of the effect when belief is absent:

When a ritual is unbelieved by the spirits present, it doesn’t matter how convinced the participants are, the ritual has no magical or deeper effect. 

Belief is an essential ingredient. To the practitioners of black magic, one of the greatest mistakes over the past thirty years was to make black magic popular into seemingly inert brands like “wicca”
 and “paganism”.

The problem is not that more living people believe in such actions and practice them, but the departed spirits know that these practitioners are just enthusiastic amateurs. This has had a negative flow on for the truly most evil of all magic practitioners in that the general release of fear towards black magic and the effect of great betrayal has in fact blunted two of their greatest belief weapons.