There are a lot of artifact appearances in World of Warcraft: Legion, at least in theory. If you’re not into pushing forward with PvP or PvE progression beyond queued content, you’re not going to be earning two of the appearances in the expansion, but there’s always the hidden artifact appearance. At least, there is if you’re not a Frost Death Knight, as a recent forum post has explained that the world boss associated with that appearance hasn’t spawned yet and thus has prevented players from obtaining that hidden appearance.
The rather lengthy post also discusses hidden appearances in general, noting that Blizzard has learned a great deal about the elusiveness of some such appearances and what has and has not worked. Players are assured that tweaks are coming in the future to make the more difficult appearances a bit easier to fine, though details are not yet available. Still, it’s good news for those searching for hidden appearances who haven’t just given up and transmogged over the artifact weapons already.