Necromancy is the practice of communing with the spirit of a deceased person or animal, or in some cases, a non-human entity. Individuals who engage in this practice are called necromancers. Necromancy usually requires some psychokinetic acumen, such as an acute knowledge of the occult, or an existing understanding and harmony with the spirit world. Those who engage in the practice of necromancy are sometimes referred to as mediums. Some necromancers may even perceive the essence of a spirit visually, whereas others may not.