mordtirith

That is the crux of the question right: what happens, with regards to the Cognitive "real form" of a spren, when they are in a gemstone? We know some spren like Honorspren can change size freely in the physical realm, while others like Cryptics can't. An Honorspren inside a gemstone might be able to just happily fit themselves in there, they can make themselves small enough the gemstone prison is a whole world for them, but take a Cryptic, usually around the size of a handspan, if they can't get any smaller and you put them on a sphere the size of a little finger nail... What does that feel like? Does it feel like anything? Navani's experiment in WaT might show that it doesn't, but as I said, we have never seen Flamespren in Shadesmar, for all we know they actually are just the size they show up in the PR, Windspren are even smaller in Shadesmar than they are in the PR. I suppose my point is less about whether spren care about their manifested size on the PR, and more about: do they care about their actual size when put in a gemstone? Does the entire spren body go into the gemstone, or just the small part that manifests on the PR, and the rest of the spren stays glued to that location?

I don't think we should use Singers for any CS physical baseline. Their anatomy is far too different from humans, they have a gemheart that was created to be filled by some piece of sentient Investiture and it radically transforms the body and, to a lesser extent, the mind (maybe the soul?) depending on what type of sentient being enters it. The Fused not fully transforming people they enter might be just that, a result of a body that has a method for it to take place. In fact, going into WaT spoilers but:

I don't doubt they'd be stuck to it, incapable of leaving the place where the gemstone is. I just wonder if, in the CR, the entire body of the spren would be locked inside the gemstone or if the rest of the spren would still manifest as usual. Locked in place by the gemstone, yes, but mostly growing around it. I think it's more likely the entire body goes in the gem, that would lend some credence to the Sibling's horror because just imagine, someone locks your tongue on a rock that is more or less the size of it and your entire body is shoved in there, that would be horrifying beyond the concept of caging them.

Would they though? I can't believe this never crossed my mind but, I don't think we've ever seen a modern fabrial in Shadesmar in the entire story... What is it like? Is the spren forced to follow the fabrial around, like a Deadeye and their bonded human? Does the spren still have its bigger manifestation? If so, using a fabrial there might get a little weird, you wouldn't just move a pen, you'd need to move a much bigger beast right? Wait we don't even know what flamespren look like in Shadesmar... Maybe they're like windspren so they'd still fit inside the gem even in Shadesmar? But if they're like painspren, I think there'd be issues

Fair, closest thing to that is the level of control the Stoneward has which shocks Szeth, but IDK if Szeth has seen many a Radiant Stoneward, maybe he just didn't expect it because Willshapers and Bondsmiths aren't that good at shaping stone. I can see the ball of light being a particular resonance for Truthwatchers, the earliest hint we have of it is when Renarin heals Adolin in OB right, Adolin gets a brief glimpse of what his perfect version would be right before he is healed at the start of the book. I can see that, Spiritual Illumination, being a result of combining Illumination with Regrowth, Regrowth lets you bring forth the internal ideal version of someone, so if you mix that with the concept of projecting images you get the "Spiritual Illumination." I still think it's likely that it is not a common skill for normal Truthwatchers though. We are told many times that people expect Renarin to be able to lightweave like Shallan, which at least to me indicates that others like the Stump are capable of doing that. I think that, for some reason, Enlightened Truthwatchers skip normal Illumination altogether and go straight for Spiritual Illumination. Maybe it'll be as hard for Renarin and Rlain to figure out how to create illusions as it would be for non-enlightened Truthwatchers to figure out how to create Spiritual Illumination?

The real question is, why did it work xD Yeah the Emperor is a figurehead, but Taravangian's goals worked perfectly fine, Azir entered the coalition and nearly came over to him in OB. Out of everything he could have done, repeatedly killing Emperors worked out just fine. How, and how the hell he knew that, is up to debate. Was that exactly his intention, to get people like Noura in power? Someone who would have enough emotion and care behind her, after repeated losses, to act on instincts of right and wrong slightly more than the "expected Azish metodology"? The repeated slaying of emperors eventually lead them to declare a miracle upon a Surgebinder, which greatly influenced them to accept the coalition of Radiants where before they seemed most afraid of the powers of all kingdoms. The bottom-line is, it worked. I think Jah Keved was an extreme exception, a land where Taravangian saw no possible path to getting them into the coalition other than him personally dragging them in via inheriting the kingdom. Remember, his "king of everything" gambit was a stupid plan because Rayse saw through it instantly, but it was supposed to be covert. The idea wasn't "Get Taravangian on the throne of every nation," instead it was "Make Odium agree to let Taravangian's lands go free, then surprise reveal that technically he is king of everything." For most governments on Roshar, just getting them into the Coalition of Monarchs was enough for his plan, and whatever he did in Azir was enough for that.

It would, and it did, Kaladin sees Szeth killing Iriali leadership in WoK. The real question is: did the Diagram realize the Iri would be leaving the planet soon? If so, maybe the leaders Taravangian had killed were those who wouldn't want to capitulate to Odium. He wanted to have everyone join the coalition, but maybe he saw 2 possible paths for Iriali: "either they fight Odium and are destroyed, or they surrender then leave. In either case, they never join the coalition... Let's just push them for the second path then." I can see that being "humanitarian" enough for Taravangian's goals. I think Taravangian wanted Elhokar to found the coalition. How much easier would it be, to push him aside and become leader, if Dalinar had died at the start of WoR and it had been Elhokar instead who took down the Parshendi and discovered Urithiru? The Diagram didn't need every nation on the world destroyed or in collapse, it needed them as pliable to Taravangian as possible. For the Vedens, yeah, that meant civil war and internal annihilation, but that didn't need to be it in every case. That even extends so far as to the Azish: Gawks was probably perfect for him, a young kid, easy to manipulate. Taravangian didn't want the entire world to kill itself, he just wanted to be in a position where he could, with as little strife as possible, get them to all go "we should put that Vargo dude in charge"

Well the metalminds Vin pushes on are almost pure godmetal too, those were Rashek's Atium metalminds. The idea is only saved by the fact that "atium was never atium", real, pure atium was unknown to Scadrians and what they called atium was an atium electrum alloy, so maybe you can say she was pushing on that? However, Brandon has already said that even Shardblades can be pushed and pulled with Allomancy, only that it'd be hard. IIRC the WoB goes over an exhaustive list of things that are metal but invested, and Shardblades were the second hardest thing to push/pull, but still possible. The hardest one was Nightblood which he said would be far harder to affect than a living shardblade.

The real question is, did he even meet her? Or is Baxil the 4th Agent of Cultivation, set on a mission as of yet unknown, probably even to himself, like Dalinar and Taravangian had no idea of the extent of what she wanted from them until much later? I don't doubt the Nightwatcher could make a CS, given what we've seen the Sibling and the Stormfather do, but Baxil's boon and curse seem so far removed from the usual. What we usually see in Nightwatcher deals are sometimes slightly oblique ways of granting the boons, and what honestly feel like almost pranks as curses. "You want to feed your family through a drought? Here, have these nice linens to sell for cash. Also now you see upside down lol." To me, Baxil's torment and extreme changes sound a lot more like Dalinar's lost memories, or Taravangian's agonizing intelligence/emotion shifts, or Lift's metabolism changing entirely.

It is possible you are right, but I don't know if we should take a human fused created by the power of Odium using the Truthwatcher Honorblade as proof of how "normal" Truthwatchers work. Renarin does question and seem genuinely puzzled at why his powers are much better aligned with the order's name than others, which to me implies he hasn't really seen unenlightened Truthwatchers doing the Spiritual Illumination he can do, otherwise there'd be no question, no puzzlement. However, it is also said that unenlightened Mistspren are very rare so who knows. Maybe Spiritual Illumination is something that all Truthwatchers can do, but it is a much harder application of the surge for those who aren't enlightened, whereas it is just second nature for enlightened ones?