Theory: Adonalsium is Nohadon and willingly "shattered"
Just some thoughts after reading the Wind and Truth about Adonalsium. Curious about your thoughts, not saying this is bullet-proof.
About the Shattering
We know that Adonalsium existed before the Cosmere and created all things (source). We can assume that he could see the future like the Shards and possibly have even greater omniescence and omnipresence.
What was he like? Why did the 16 go with the plot to kill him? Some wanted power but some were genuinely good people to whom it seemed like the only option left. I hypothesize that he was a "micromanaging" God albeit with good intentions. This led to a level of intrusion into the mortal affairs that people found unacceptable - they wanted free choice.
The on the nose explanation of what happened is that the 16 who shattered Adonalsium outsmarted and killed him. This seems suspect to me given his own omniescence and power.
The alternative I propose is that Ado reflected on the reasons of the people wanting to kill him and found some of them valid. He questioned his role up to that point in the affairs of Cosmere and allowed himself to be shattered.
Where's Ado
Adonalsium stepped down from ruling the Cosmere by letting himself be shattered. But he didn't "die" in the process,The assassination was an impetus for him to self-reflect on his role in the Cosmere. He went from being a micromanaging God (like Old Testament God) to a "wise witness" God (like New Testament / Christian God).
My guess is also that he is not powerless after Shattering but being the all-powerful Cosmic Creator and source of everything, by being Shattered, he simply willingly invested the Vessels with his power through Shards (like Honor invested the Heralds) and could reclaim that power at any moment should he choose to (well that was my guess, I don't think anything in the text supports that strongly. Thanks @wormotif for pointing out why it's unlikely. On the other hand Nohadon = Ado seems to have a lot of evidence in the text). But he wants to let his people rule themselves now (like Nohadon did for a time) and listen instead.
This parallels the human king Nohadon's personal journey and reflections on ruling and his reflections in Way of Kings are applicable to the human king as well as the cosmic deity.
Nohadon in Wind and Truth visions is Adonalsium
Note: Nohadon = No-h-Adon = No-Lord (No = negation as in English, Adon = Lord in Hebrew).
In Wind and Truth Dalinar encounters Nohadon in his visions of the Spiritual Realm. This entity pulls him out of his final encounter with the god Todium without the god noticing anything. That’s a pretty big sign that he’s at least a Shard level power. It could be Dalinar’s mind itself but Nohadon doesn’t seem to be a figment of Dalinar’s imagination. He serves him buttered bread which Dalinar has never eaten before so has no way of imagining it. Dalinar seems to come to the same conclusion:
So if he’s a different Shard+ level power then which one? Possible Shard candidates are Reason and Valor about whose location we know little. But Nohadon's advice (to the degree that he explicitly even offers any) is very balanced and rings with wisdom. While we’ve seen that a Vessel can overpower a Shard’s intent I’d expect at least some of that itent to shine through in an extended conversation and I didn’t notice any Reason or Valor impulses here. Additionally, if we look at the actual life of the king Nohadon and his book The Way of Kings - the argument that he would be one of these Vessels grows very weak. He doesn’t write like a person guided by an extreme of a single Intent but rather with a wise balance.
There is only one other being with this power level that we know of - he is some part of Adonalsium himself. We’ve seen in the book that there are parts of him that remain - the Wind, Stone and Night on Roshar. So it’s not unthinkable this could be another "part" of him - potentially the primary part. And note that we do not know how powerful that could be.
Is king Nohadon the same being as vision Nohadon?
If so, that would make him Adonalsium incarnate. Did (some part of) Ado decide to incarnate in Roshar to learn more about mortal lives? Did he make himself forget his godly nature for a time or was he aware of it?
Or was the king Nohadon simply a human king who reached similar conclusions to ruling that Ado did. I am inclined towards them being the same entity.
Some text evidence for king No-h-Adon = Adonalsium
On first reading these words they refer to Nohadon's journey by foot when he deserted his kingship for a time. But they seem even more relevant to a God recognizing the day to walk away and abandoning his throne and gifting his people with his absence so that they grow to solve their own problems.
Who better for Tanavast (a god) to study than the actual God?
Dalinar shares a meal (bread with butter) with Nohadon in his final vision before Dalinar abdicates the power of Honor. Nohadon also doesn't say who he is even though Dalinar explicitly asks him (see next quotation). He lets Dalinar pass with two lies.
Nohadon asks Dalinar to consider what "Nohadon" would do in Dalinar's situation (being in possesion of divine powers but unsure of how to apply them for the good of everyone). Later, Dalinar seems to follow Nohadon's unspoken advice and abdicates his divine powers. Just like I suggest Adonalsium did (and the king Nohadon did for a time).
In a subsequent paragraph, Dalinar (and the reader) questions the king's identity - implying he might not be who he "obviously" seems to be.
After that Dalinar notes he doesn't feel like a god but a man talking to another man. In what situation would Dalinar (a god) feel this way? Maybe when talking to another god / God.
When Taravangian tries to claim Dalinar's soul before it passes into the Beyond, he is denied. The being that Dalinar interacts with seems to be the most likely candidate by whom he is claimed (thanks @adouloumis for pointing this out).
Finally, let's consider this Tanavast's stream-of-consiousness when he begins to question the actions he's taken as a deity:
Tanavast asks the Wind (a part of Adonalsium) what he should do. It tells him to listen. He stops micromanaging (leading, organizing, pushing) and for the first time in his divine existence it all start to make sense. He is needed as a witness. They might be better off without him. Could Adonalsium have come to a similar conclusion?
Note that while compared with Tanavast, the Wind still considers Adonalsium to have been a caring God but it's possible to have an overbearing and still well-intentioned caring God.
I also want to shine a light on this part of the above quote:
At first glance it is just another in the enumeration of random individuals Tanavast witnesses (the woman milking hogs, the child, the scholar, the wanderer) but it has a double meaning - Tanavast is also a wanderer on a god's journey and unwittingly walks the same path of listening that No-h-Adon has taken up after the Shattering.
Thanks for reading, looking forward to your thoughts.