Diablo III devs decided to pay homage to an artist that worked on World of Warcraft and Diablo, that passed away two years ago, but sneaking a little event into Diablo III.
It’s basically a version of the famous Cow level. It’s quite easy to unlock when compared with other Diablo III Easter Eggs. Simply go to Immortal Throne in Act III’s Ruins of Sescheron. The room in the west-northwest part of the level is the throne room. Kanai’s soul will awake and open a portal to the Easter Egg.
Check out this video by MadTom for a tutorial.

Kevin Kanai Griffith was the artists name who passed in October 2014 from a rare form of cancer. Props to the Diablo III team for honoring this dedicated artist and member of the team.