All you have to do is locate all the Marble Maiden Tribute locations, they are a ‘?’ location once you find it the ‘?’ Icon will then show as a statue icon, then destroy the statue.
Links for each region.
Pheraia's Retreat
https://guides.gamepressure.com/assassins-creed-odyssey/guid...Deukalion's Heritage
https://guides.gamepressure.com/assassins-creed-odyssey/guid...Minos's Faith
https://guides.gamepressure.com/assassins-creed-odyssey/guid...Asphodel Fields
https://guides.gamepressure.com/assassins-creed-odyssey/guid...