the most common practice for a necromancer is to summon the spirit of the corpse by sacrifices and incantations. The rituals demand meticulous execution and exacting preparations involving the choice of a proper place, for example a cemetery or the ruins of an ancient monastery; the choice of the right time, usually between the hours of midnight and one in the morning; use of specific incantations; and accessories, such as bells. One of the most important elements is the use of a magic circle which protects the necromancer and his or her assistant from being harmed by provoking the dead.
when summoning the dead, it's imparative to get into the right frame of mind. the necromancers surround themselves with the aura of death for nine days, dressing in the dead person's clothes or wearing a token of theirs while eating food that represents decay, like black bread. some are known to eat the flesh of dog as it is a creature of hecate, the goddess of ghosts and death and sterility. the black bread and drinking unfermented grape juice is a necromantic equivalent of the bread and wine of communion, and is considered a sacrament of emptiness and despair.
through these preparations the necromancer puts themselves in touch with death, into a corpse-like state in which they are in rapport with the real corpse they intend to disturb. they will burn torches and burn a mixture of henbane, hemlock, aloes wood, saffron, opium and mandrake.
they will read the rites of hecate, and arrange the body with its head to the east, the direction of the rising sun, and with its arms and legs in the position of the crucified christ, so that it will rise from the dead. they will light a dish of wine, mastic and sweet oil to conjure the spirit to enter its old body and speak. in some cases, the dead are summoned to attack a person the necromancer wishes to harm or master. they also resurrect for the purpose of answers; foretelling the future, or for the witch to carry out its unfinished business in exchange for something in return, usually jewels or relics buried inside the coffin.
some necromancy rituals require a sacrifice but that doesn't always refer to killing a person. offering hair or blood was a substitute for a sacrifice, though they often used animal blood in the process. many necromancers chose sympathetic magic when making requests of spirits. As an example, knocking two rocks together demonstrated the feud they wanted the spirits to start between two families.
Some necromancers used a system more recognizable to us as a form of spiritualism. The necromancer invited a spirit into a medium, using the medium like a ventriloquist’s dummy. Famed Elizabethan magician John Dee used Edward Kelley as his medium when speaking to angels. Under Redgrove’s definitions of medieval ceremonial magic, their seances were closer to white magic since they involved angels.
some say necromancers might mutilate or eat corpses though that’s unlikely in the medieval period. These magicians used spells and incantations with a linguistic structure similar to those used in exorcisms. They took these rituals very seriously.