One is the Cube room, but the other room nearby is the Immortal Throne, where ghost barbarians line the way to a barbarian skeleton sitting on a throne. There are two important mini zones or rooms in the Elder Sanctum, which is in the Ruins of Sescheron, where you go to get Kanai’s Cube at Zoltun Kulle’s request. The developers answered a creation question about the namesake of Kanai’s Cube that confirmed some of my suspicions from the PTR. I’m not sure this is referring specifically to the Cube itself, though - it might be referring to Kanai. There was a non-comment about hidden Cube recipes. Reddit user jiminee suggested having tooltips on items to know if you’ve extracted that legendary power yet or not, and Lead Designer Kevin Martens agreed that they’d look into that.

Seasonals, however, still need to earn those many level 70 elite kills, and the recipes like Hope of Cain that involve a lot of Death’s Breath are aimed at more avid seasonal players who want more control over specific slots when it comes to gaining gear pieces. Nonseasonal characters probably have Death’s Breath stockpiled due to much less use in older patches, which made Kanai’s Cube particularly fun when Patch 2.3.0 launched as players could use the recipes right away. The developers are happy with the costs of some recipes because they make Death’s Breath a crafting material that’s worthwhile to farm and gather again. Ancient items will continue to be a random extra thing that avid players can strive for, and there are no plans to add a make-a-Ramaladni’s Gift recipe to the Cube. The Cube is built to be expandable, so we may see more recipes down the road. The general developer reaction to questions about Kanai’s Cube is positive, as if they’re satisfied with how the Cube has worked out so far. Although the original Q&A thread is here, r/Diablo moderator Menagese compiled a brief summary link list of the Q&A that makes it a little easier to find specific answers.

The Diablo 3 developers held an AMA-style Reddit Q&A on September 1st, a week after Patch 2.3.0 launched and after the opening weekend for Season 4.

Reddit diablo 3 builds