Mediums contact dead human beings.
God interacting with His creatures through the Holy Spirit is not necromancy or sorcery.
Scripture is adequate but the man without the Spirit cannot understand spiritual truths as they are spiritually discerned, which is why none of what we've been telling you about God and Scripture makes any sense to you.
I have heard it said that the Bible is a “letter” to Christians. I believe it was Chuck Missler.
The point being that the unsaved are equipped to understand the Gospel messages for salvation, but not much more.
None the less, we have many “learned” posters here that intellectualize constantly [some are educated beyond their intelligence] to “explain” what the Bible means but end up mostly believing their traditions which lead them into darkness, and to the Catholic Mary.