There are a great number of artifacts that are scattered around D'ni and its Ages. These artifacts come in different forms, clothing left behind by the D'ni and DRC (and in some case holiday hats left specifically for explorers) to Relto Pages which are left by Yeesha that change the Age of Relto, adding things like weather, tapestries and other things.
Below is a list of the various kinds of artifact, where they can be found and what additions they add.
Calendar Roses - Each month a new "spark" appears in one of the Ages of D'ni adding a Calendar Rose to Relto.
Cannen Music - The cannen in Relto can have extra tracks added to it that can be picked up when exploring.
Clothing - Various items of clothing can be found throughout D'ni and it's Ages.
Relto Pages - Relto Pages can be found throughout D'ni and its Ages adding new aspects to Relto.
Stone Wedges - Strange stone wedges that can be obtained via the various Bahro Caves.