It might not be possible to create, or arrange, or organise such a power in our own time; but I take it that if in Old Time such a power existed, it may have some exceptional survival.

After all, the Bible is not a myth; and we read there that the sun stood still at a man's command, and that an ass--not a human one--spoke.

And if the Witch at Endor could call up to Saul the spirit of Samuel, why may not there have been others with equal powers; and why may not one among them survive?
Indeed, we are told in the Book of Samuel that the Witch of Endor was only one of many, and her being consulted by Saul was a matter of chance.

He only sought one among the many whom he had driven out of Israel; 'all those that had Familiar Spirits, and the Wizards.' This Egyptian Queen, Tera, who reigned nearly two thousand years before Saul, had a Familiar, and was a Wizard too.

See how the priests of her time, and those after it tried to wipe out her name from the face of the earth, and put a curse over the very door of her tomb so that none might ever discover the lost name.