“Sphinx” is a transliteration of “Sheshep-ankh”, living image.
Sheshep-ankh-en-Amun Setepenre was actually one of the kings of Meroe in the 3rd c BC — well after the 25th dynasty was booted from Egypt.
But why make the king look like a sphinx? He never was a sphinx do they think he is in the afterlife one?