It is a good idea not to have too many enemies in Djenne. While the population is gentle and agreeable for the most part, and as good Muslims they resign themselves to the will of Allah, there are also those who are not adverse to indulging in a little magic in order to get their way. There is a flourishing trade in potions and elixirs, spells and gri-gris or talismans imbued with power for good or ill.
This trade is largely the monopoly of the marabouts, ostensibly holy men, well versed in the intricacies of the Koran, which they teach to the talibés, the little beggar boys in their charge at the numerous Koran schools of Djenne. Often marabouts make a lucrative side-line as purveyors of magic potions.
There are potions for all ills- physical and metaphysical. There are potions to make people love you, and to make them stop loving someone else for instance. Such means of persuasion are not the prerogative of Africans, but plenty of westerners avail themselves of these ancient African methods. A very handsome young Canadian I met when I first arrived in Djenne whose girlfriend had dumped him went to a marabout to make her love him again. Since the girl was in Bamako the use of potions on her was not a practical option but that did not present a problem- there are gri-gris that can be applied at a distance.
I am not certain of the outcome for the love-lorn Canadian, but I have just heard a chilling story which bears all the marks of veracity and was reported on national radio:

A young wife went to a marabout to obtain a potion to give to her husband in order to prevent him from taking a second wife. The marabout liked the look of her and decided he wanted her for himself. He gave her a potion which she promptly dispensed to her husband, who fell ill of a mysterious decease and died within two days. The wife was hardly in a position to say anything. After the prescribed time of mourning the marabout made her a visit and was politely received. He began courting the young widow, who soon invited him for dinner one night. At the end of the evening he began to feel unwell. The widow said: ‘the potion you gave me was not used up- I gave you the remaining half in your dinner.’
The marabout died within two days. The reason we know this story is that he didn’t want to face Allah without making amends- he had the time to go to the gendarmerie to give himself up before he expired..