From GameWatcher: “With Anthem in its full live service swing, Bioware are starting to introduce new elements to their third-person shooter. Anthem Elysian Artifacts are one of the additions introduced in the latest patch as rewards to completing Strongholds. However, in order to open the chests that hold them you’ll need to find Anthem Elysian Artifact Keys.”
Source: N4G PC Anthem Elysian Artifact Keys Location