Diablo's 20th Anniversary


 * "Strange things are afoot in the world of Azeroth as denizens of Sanctuary cross over into an unfamiliar world."

Diablo's 20th Anniversary was a world event celebrating the 20th anniversary of the Diablo franchise. The event lasted one week, running from January 4-9, 2017. Players on EU servers reported the event going live on January 3rd. The event actually lasted through the 10th, however, so the ending date in the announcement may have been in error.

During the event, players would sometimes encounter Treasure Goblins at the end of Legion dungeons or out in the Broken Isles. Successfully killing a Treasure Goblin allowed players to enter a portal to the "Secret Cow Level", a phased version of the Yorgen Farmstead in Duskwood inhabited by demonic bovines and the dreaded Cow King. Although the Cow King could only be killed and looted for unique Diablo-themed items once per character, players could farm the Treasure Goblins.

NPCs

 * s summoned by demonology warlocks temporarily used the Mini Diablo model

Achievements

 * Diablo's 20th Anniversary (achievement)