The ORDIR gives the following Redemption definition of an idol:
A card is an idol if it represents a statue or physical representation of a false god.
Note that this does not specify artifact.
Many ancient kings set themselves up as false gods. Pharoahs in Egypt were believed to be representations of Horus. Augustus Cesar (the one who called the census that sent Mary and Joseph to Bethlehem) issued coins that had his face on one side and "lord and god" on the other. Nebuchadnezzar set up an image of himself, and when Shadrach, Meshach, and Abednego didn't worship him he threw them into the furnace.
I submit that these characters should be considered idols for Redemption purposes. Discuss.
What no I'm not just trying to search for Nebby with Endless Treasures why do you ask