The Ad Oblivione mentioned by Aranara is what makes them forget so they give 'living memories' to remember Ad Oblivione is related to Wind and the Erosion of Memories and this might be the Erosion that the heavenly principles Imposed to all the creatures of Teyvat

It is the power of Istaroth, the Shade of Wind and Time Ad Oblivione means 'the Wind that flows forever' and 'the Thousand Winds that return to one'