How do I create an artifact based on an existing one?

via Artifacts.xdb, and you need to modify it. Find the desired item there; for the dragon shield, it's DRAGON_SCALE_SHIELD. To change the name, you need to modify the NameFileRef and DescriptionFileRef lines to your own, or change the entries in the existing files for this artifact. Yes, this will affect all maps, but there's no other way to do it.