What don't we know?

[JoelyWoely he/him]

By this I mean what do we know exists, but haven't found? For example we know there's a worldhopping Kandra we've seen at least once I think, stuff like that.

[Khyrindor he/him]

There are six Shards of Adonalsium we can only guess the names of.

Vax? Where is it? When will we see it?

Silverlight. We know a bit. It's a city in the cognitive realm, there are universities there that Khriss helped found, and many people live their whole lives there without going to actual planets. But we haven't seen more than mentions thus far.

Dragonsteel? Is it still canon? Who knows.

[Weltall]

- Along with Vax, Obrodai is another world that we know exists but we know very little about it at present. Brandon has actually danced around the question of whether Vax is an entire world or just a place on a world, but given the context it's almost certainly the former and he's just being trolly.

- Hoid apparently has a base of operations somewhere in the Cosmere when he's not hanging around any particular world but we don't know where that is.

- Actually, let's just say 'Hoid' as a general category. We know for example that he's the second-oldest living being in the Cosmere and he started out as human but we don't know how he's managed to live so long. We know he was present for the Shattering of Adonalsium and knew all the Vessels personally but we don't know most of the details, we certainly don't know his motivations... but that may be getting off track for what you're thinking of in terms of 'known unknowns'.

- Brandon has left open the question of whether we've seen dragons 'onscreen' (setting aside Frost and Hoid exchanging letters) but told us that there are dragons off of Yolen and if we have seen one, we wouldn't recognize them. So sort of like the kandra worldhopper we may have a dragon worldhopper lurking in the pages.

13 hours ago, Khyrindor said:

Dragonsteel? Is it still canon? Who knows.

We know the answer to this one is 'No' with an asterisk. Even if Brandon hadn't told us so directly, it simply can't be canon as-is because he lifted the Shattered Plains sequence from it to give Kaladin the story he needed when he rewrote Way of Kings Prime into the book that we know today. Here's a representative WoB:

Quote

Questioner [PENDING REVIEW]

For a hardcore fan, one clue you'd give out... [About] Hoid, or Dragonsteel, or Restares.

Brandon Sanderson [PENDING REVIEW]

...The problem is, so little of Dragonsteel is still canon. I've pulled so much out of it.

The Sho Del are still canon, and Hoid has an interesting relationship with several of them.

source

The asterisk comes from how some of the worldbuilding in the revealed Dragonsteel material is still canon to some extent (like the Sho Del) but the individual characters aren't, anything to do with Yolen's gods is up in the air, Hoid's role apparently is too and even the titular dragonsteel hasn't been firmly nailed down in Brandon's head yet.

[Khyrindor he/him]

@Weltall I meant the metal Dragonsteel, not the story itself. I should have been more clear. 

Another thing I'd like to add is how smaller cognitive reflections work between worlds. How do gas giants, stars, and other planetary bodies look in the cognitive realm? We know they do, but have no idea how. 

Also, the third continent on Sel. We have the Fjordell/Arelene continent, the Rose Emipre continent, and a third that we know absolutely nothing about thus far.