Hidden Artifact Appearances, A Note from the WoW Team, Warlock Q&A Followup, DLC #551 - MMO-Champion
Legion - Artifact Weapons - MMO-Champion
Hidden Artifact Weapon Appearances and Effects - Wowhead
Many players would still be playing if there was a continuation to this system: one where you unlock appearances through activities and achievements, not just item drop / RNG. Pursuing artifact appearances
Hidden Artifact Weapon Appearances and Effects - Wowhead
Legion - Artifact Weapons - MMO-Champion
Missing Feral Artifact Form?
Hidden Artifact Weapon Appearances and Effects - Wowhead