Under the cover of darkness Saul and his attendants made their way across the plain, and, safely passing the Philistine host, they crossed the mountain ridge, to the lonely home of the sorceress of Endor. Here the woman with a familiar spirit had hidden herself away that she might secretly continue her profane incantations. Disguised as he was, Saul's lofty stature and kingly port declared that he was no common soldier. The woman suspected that her visitor was Saul, and his rich gifts strengthened her suspicions. To his request, “I pray thee, divine unto me by the familiar spirit, and bring me him up, whom I shall name unto thee,” the woman answered, “Behold, thou knowest what Saul hath done, how he hath cut off those that have familiar spirits, and the wizards, out of the land: wherefore then layest thou a snare for my life, to cause me to die?” Then “Saul sware to her by the Lord, saying, As the Lord liveth, there shall no punishment happen to thee for this thing.” And when she said,…
"Then said Saul unto his servants, Seek me a woman that hath a familiar spirit, that I may go to her, and enquire of her. And his servants said to him, Behold, there is a woman that hath a familiar spirit at En–dor."
EGW directly quotes and references 1 Samuel 28:7, describing Saul's request to find a woman with a familiar spirit at Endor.
"After practicing her incantations, she said, “I saw gods ascending out of the earth.... An old man cometh up; and he is covered with a mantle. And Saul perceived that it was Samuel, and he stooped with his face to the ground, and bowed himself.” PP 679.2"
"And he said unto her, What form is he of? And she said, An old man cometh up; and he is covered with a mantle. And Saul perceived that it was Samuel, and he stooped with his face to the ground, and bowed himself."
EGW directly quotes and references 1 Samuel 28:14, describing the woman's description of Samuel and Saul's reaction.
"It was not God's holy prophet that came forth at the spell of a sorcerer's incantation. Samuel was not present in that haunt of evil spirits. That supernatural appearance was produced solely by the power of Satan. He could as easily assume the form of Samuel as he could assume that of an angel of light, when he tempted Christ in the wilderness. PP 679.3"
"And no marvel; for Satan himself is transformed into an angel of light."
The EGW passage directly alludes to the concept of Satan transforming himself into an angel of light, as described in 2 Corinthians 11:14. The context in PP is about Satan impersonating Samuel.
"And when the tempter came to him, he said, If thou be the Son of God, command that these stones be made bread. But he answered and said, It is written, Man shall not live by bread alone, but by every word that proceedeth out of the mouth of God. Then the devil taketh him up into the holy city, and setteth him on a pinnacle of the temple, And saith unto him, If thou be the Son of God, cast thyself down: for it is written, He shall give his angels charge concerning thee: and in their hands they shall bear thee up, lest at any time thou dash thy foot against a stone. Jesus said unto him, It is written again, Thou shalt not tempt the Lord thy God. Again, the devil taketh him up into an exceeding high mountain, and sheweth him all the kingdoms of the world, and the glory of them; And saith unto him, All these things will I give thee, if thou wilt fall down and worship me. Then saith Jesus unto him, Get thee hence, Satan: for it is written, Thou shalt worship the Lord thy God, and him only shalt thou serve."
The EGW passage draws a parallel between Satan's ability to assume different forms (Samuel) and his temptation of Christ in the wilderness, where he also used deception. Matthew 4:3-10 describes the temptation of Christ.