Nahantu and some rookie mistakes/gaps in knowledge

Hey all,

I’ve been playing Diablo for the last 25 years, so am pretty well versed in things. But I have two questions that Google/icyveins/wowhead/Reddit haven’t really been able to answer (and I am too old to rely on 20 minutes YouTube videos). Any help would be massively appreciated:

  1. when a world boss spawns in Nahantu, I can’t get there. I have 56 out of 58 locations. The two missing areas look to be a smaller one and a larger one. I assume the larger one is “the cauldron” and where the boss is spawning. There seems no way in. Is it simply locked behind story mode and I need to progress that?

  2. the co-op dungeon the citadel. I will create/join a random group and we will make it to Gorshak but then come completely undone. There seems to be a timer (“impending doom?”) and a gateway. I can take Gorshak down to the invulnerable stage and then get into the other realm with the two altars and the stones. But for the love of god I can’t seem to do anything, I end up with one stone and no altar that will take it? I’m missing something very obvious.

Other than that, I want to go on record and say d4 has been exceptional and every season has made it better. (But I’m somebody who loved d3 and put 800+ hours into it, so I’m biased)