Question: "What does the Bible say about necromancy?"
Necromancy is defined as the conjuring of the spirits of the dead for purposes of magically revealing the future or influencing the course of events. In the Bible, necromancy is also called “divination,” “sorcery” and “spiritism” and is forbidden many times in Scripture (Leviticus 19:26; Deuteronomy 18:10; Galatians 5:19-20; Acts 19:19) as an abomination to God. It is something that the Lord speaks very strongly against and is to be avoided as much as any evil. The reason for this is twofold.
First, necromancy is going to involve demons and opens the one who practices it to demonic attack. Satan and his demons seek to destroy us, not to impart to us truth or wisdom. We are told that our “enemy the devil prowls around like a roaring lion looking for someone to devour” (1 Peter 5:8). Second, necromancy does not rely on the Lord for information, the Lord who promises to freely give wisdom to all who ask for it (James 1:5). This is especially telling because the Lord always wants to lead us to truth and life, but demons always want to lead us to lies and serious damage.
The idea that dead people’s spirits can be contacted for information is false. Those who attempt such contact inevitably contact demonic spirits, not the spirits of dead loved ones. Those who die go immediately to heaven or hell—heaven if they believed in Jesus as Savior, and hell if they did not. There is no contact between the dead and the living. Therefore, seeking the dead is unnecessary and very dangerous.