Ancestral spirits can be the personal ancestors of the sangoma or the patient or they might be general ancestors associated with the geographic area or the community. It is believed that the spirits have the power to intervene in people's lives who work to connect the sangoma to the spirits that are acting in a manner to cause affliction. For example, a crab could be invoked as a mediator between the human world and the world of spirits because of its ability to move between the world of the land and the sea. Helping and harming spirits are believed to use the human body as a battleground for their own conflicts. By using ngoma, the sangoma believes they can create harmony between the spirits which is thought to bring an alleviation of the patient's suffering.