He inquired of the LORD, but the LORD did not answer him by dreams or Urim or prophets. Saul then said to his attendants, "Find me a woman who is a medium, so I may go and inquire of her." "There is one in Endor," they said. 1 Samuel 28:6-7
This is certainly a troubling passage for Christians and rightly so. There's a lot we don't know in this passage. Did Saul actually hear Samuel and did the medium actually see Samuel? Was the voice of Samuel telling the truth about the kingdom being ripped out of Saul's hands and into David's?
Saul knew that he had turned his back on God; Samuel knew it; David and Jonathan knew it. And yet Saul tried to get answers from the Lord about what he should do next in battle against the Philistines. He got nothing, so he consulted a medium. Again, the voice of Samuel confirmed that he was turning away from the Lord.
I don't know a lot about the spirit realm, but I do know this: Christians ought not to be dabbling into divining the truth from someone other than God. If we don't get an answer from God on a matter, keep asking. Keep bugging God for your answers. You'll find that that's what He wanted you to do all along.