The Sherbro believe that all deaths and diseases, other than those caused by obvious acts of violence, can be attributed to potent ‘medicines’ or witchcraft. This witchcraft is thought to be activated whenever the conventions of a certain ‘medicine’ have been contravened or violated.

However, as well as coexisting with these ‘medicines’, the Sherbro people also believe that each has an antidote that can only be administered by the person or being who controls it. Therefore, whenever one gets sick, they must consult with a diviner who will determine what ‘medicine’ has caused their ailment. The diviner will then advise that they appear before the ‘medicine’ in question to confess to a transgression and offer compensation before they can receive the antidote.

Most treatments or cures are created and developed by certain associations. The Sherbro association known as the Yase or Yassi is with curing both physical and mental disorders.

Other common associations in Sierra Leone and western Liberia include the Poro and Sande. These associations are distinguished from one another by their possession of these 'medicine' figures. Meanwhile, ranking within associations is denoted by spots. Almost all things owned by the Yassi are spotted, from houses and weapons to musical instruments. The only exception to this is their wooden minsereh figures which are entirely black. These minsereh figures are communicated with by Yassi diviners to determine cures for ailments and establish what treatments should be administered.