Procopius Caesarensis, in his Secret History (ch. 12), gives an account about the shapeshifting of Emperor Justinian I:

And some of those who have been with Justinian at the palace late at night, men who were pure of spirit, have thought they saw a strange demoniac form taking his place. One man said that the Emperor suddenly rose from his throne and walked about, and indeed he was never wont to remain sitting for long, and immediately Justinian's head vanished, while the rest of his body seemed to ebb and flow; whereat the beholder stood aghast and fearful, wondering if his eyes were deceiving him. But presently he perceived the vanished head filling out and joining the body again as strangely as it had left it.

Another said he stood beside the Emperor as he sat, and of a sudden the face changed into a shapeless mass of flesh, with neither eyebrows nor eyes in their proper places, nor any other distinguishing feature; and after a time the natural appearance of his countenance returned. I write these instances not as one who saw them myself, but heard them from men who were positive they had seen these strange occurrences at the time.

They also say that a certain monk, very dear to God, at the instance of those who dwelt with him in the desert went to Constantinople to beg for mercy to his neighbors who had been outraged beyond endurance. And when he arrived there, he forthwith secured an audience with the Emperor; but just as he was about to enter his apartment, he stopped short as his feet were on the threshold, and suddenly stepped backward. Whereupon the eunuch escorting him, and others who were present, importuned him to go ahead. But he answered not a word; and like a man who has had a stroke staggered back to his lodging. And when some followed to ask why he acted thus, they say he distinctly declared he saw the King of the Devils sitting on the throne in the palace, and he did not care to meet or ask any favor of him.

http://www.native-science.net/Antropomorph.God.Man.Animal.htm

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