The conjuring of the spirits of the dead for purposes of magically revealing the future or influencing the course of events is totally against the wishes of God.
Necromancy involves demonic practice and opens up the door for Satan to come into our lives and influence it negatively. The Devil wants to destroy us; he does not give truth and wisdom; that is why God finds these Satanic practise an abomination.
Ecclesiastes 9:5-6, For the living, know that they shall die: but the dead know not any thing, neither have they any more a reward; for the memory of them is forgotten. 6 Also their love, and their hatred and their envy have now perished; neither have they any more a portion for ever in anything that is done under the sun.
Leviticus 19:31 Regard not them that have familiar spirits, neither seek after wizards, to be defiled by them: I am the Lord your God.
Leviticus 20:6 And the soul that turneth after such as have familiar spirits, and after wizards, to go a whoring after them, I will even set my face against that soul and will cut him off from among his people.
Jeremiah 27:9 Therefore hearken not ye to your prophets, nor your diviners, nor your dreamers, nor to your enchanters, nor to your sorcerers, which speak unto you, saying, Ye shall not serve the king of Babylon.
2 Kings 21:6 And he made his son pass through the fire, and observed times, and used enchantments, and dealt with familiar spirits and wizards: he wrought much wickedness in the sight of the Lord, to provoke him to anger.