Artifacts are a feature in SteamWorld Dig 2, requiring you to look for secrets in caves and around the play area. There are a total of 42 artifacts in SteamWorld Dig 2, however if you count the extra artifact in the Trial of Crushers there is 43 artifacts.
When collecting artifacts a speech bubble with a green figure might pop up above a character in El Machino. This means that you can get a free blueprint for a cog mod if you talk to that character