Artifacts are a collectible found within Legend of Minerva. They come six to a set and are typically found via questing. There are also special sets that are tied to events.
Collecting all the items in a set will reward you with a powerful Eidolon Card. You can only collect up to 100 of each artifact. Any more will be thrown away.
Each set may only be turned in once, and other players can battle you to take your artifacts.