Albert Barnes Commentary 1 Samuel 28:13

"And the king said unto her, Be not afraid: for what seest thou? And the woman said unto Saul, I see a god coming up out of the earth." — 1 Samuel 28:13 (ASV)

Gods - The word אלהים ('elohim) is used here in a general sense for a supernatural appearance, such as an angel or spirit. Hell, or the place of the departed, is represented as being under the earth (Compare to 1 Samuel 28:19 and 2 Samuel 12:23; Ezekiel 32:18).