Quantus

I like it. We have the example of the Horneaters that are part spren, and the Royal Locks that are part Returned, so that's at least two instances of Cognitive entities breeding with physical ones to a noticeable effect. I like the idea of it being Threnodite, Im curios if being a half-shade would be at all possible. I think Id be hesitant to use to much etymology for this sort of thing in the Cosmere, if only because of the weird ways Connection can play with a person's language skills, something that would basically have to come into play for worldhoppers.

I agree with what seems to be the general consensus. The Honorblades appear to provide two separate things: The Ability to use the Surges, and a direct connection to the Spiritual to bypass the normal Stormlight cycle ecosystem. The best cosmere analogies I can think of are Unsealed Medallions for the former, and a Mistborn using the Mists to directly fuel Allomancy for the latter. I do have a question: The OP mentioned that the Honorblades allowed the Heralds to use the surges "in a far more powerful manner". I thought that was not the case, that they allowed the Heralds to Channel far more Stormlight than a Radiant, but that their Surges themselves were far less efficient in their energy so it more or less balanced out to the same overall capabilities? I was thinking that Nale might get a significant advantage by having access to both options, having an Honorblade to provide boatloads of Investiture, and a sentient Bonded spren to manage that excess Investiture into Surges efficiently like Radiants (not unlike the difference between Fabrials and Radiants using a given surge).

Suffocation? Given that it takes a separate Metal to store Breath, they'd be left healing the actual cell damage from asphyxiation as it accumulates, and it should run down their reserves with a problem they cannot permanently solve with the Gold. It would probably take longer than setting them on Fire, and if they are desperate a Self-Tracheostomy might still get them past whatever strangulation tools were used. But it's a reasonable "Hang on until they stop twitching" method, would be slow but technically possible.

The "extra" power is from the difference between a mundane metal and a Godmetal which is pure condensed Investiture. On the feruchemical side you are still using the Atium as just a Storage Device, while on the Allomantic side you are still obliterating the metal itself and converting it to pure Investiture. The difference (as I currently understand it) is that burning a mundane metal only releases enough Investiture to create a conduit to Preservation's store of Infinite Investiture, while a godmetal has enough energy density to provide the entire effect. That would be the case regardless of whether the Atium is being burned normally or if it was pre-charged by Feruchemy first to force that released Ruin energy to behave like Youth-Storage Investiture rather than Fortune-based Future Shadow Investiture.

You could use the Tears of Edgli as the symbol, and go floral patterns with lots and lots of colors.

Flashbacks and/or offscreen event with a new character? Speaking in ignorance of the story specifics or the scope of the retcon plan, you say your issues boil down to three parts: You need more world-building, you need more character development, and your characters need the characters to have more time to establish relationships. The first two you could theoretically do with a flashback chapter or two, have them remembering and/or retelling some personal events that may or may not have related to the Major Plot (or did tangentially but they didnt realize it at the time, maybe). The third one harder, it's not easy to just invent more time for them to settle into relationship patterns. What could work for all of these is to flashback and introduce a new character, one with relationships to each of the ones you wanted to have more time; one shortcut to them getting to know each other is a mutual acquaintance (not necessarily friend). So you take some time to introduce this new character in some flashbacks with the other characters (doing whatever character and world-building that makes sense), then tie it back in with a Meanwhile Chapter that informs the reader what they've been up to during the current actions of the main group, until eventually their paths cross. The other characters wont have relationships with each other, but they will with this new support character which will pull them together, skip some of the team-building needs, and force them to get to know each other against and/or relative to this new character. They become the nucleus of the group until the others have their moments to develop deeper direct relationships. It's adding the complication of a new character, but it offers a way to justify the flashbacks and new characterizations, and give you more background screen-time to world-build, without having to actually retcon the series of events to make it happen all with the current stable of characters. Again, I dont know if that's workable with your specific case, but it might be a roundabout path forward.

Hmm, defined as just a sensory illusion, I can get behind that. Capsaicin is literally no damage though, even when hitting other mucus membranes like the eyes? Because if he cannot punch himself but he can pepper-spray himself, that's an oddly comical distinction.

I was re-reading the scene in OB with Shallan and Hoid, and it mentioned in passing that they served the food with male and female seasonings on the side, Sweet for her and Spicy for him, as the Rosharan gender foods dictate. That made me wonder, have we ever seen Hoid/Wit eat "Masculine" food? I ask because Masculine food is very Spicy, and Spicy is not actually a Flavor, it is actually Pain Response that we basically just enjoy enough to seek out. Which means eating Spicy food is technically self-inflicted Damage, something we now know Hoid is incapable of. Along those lines, we know he becomes sickened to the point of incapacitated if he considers hurting himself. Can he do it by accident? Is he even capable of Accidents with his super-special Fortune effect? If he makes Tea, will he instantly Know the moment his cup of tea has cooled off enough that it will not scald his mouth?

Dont forget the ChayShan, it's entirely a magic martial arts and being another Dor-based "programming language to hack reality" it could theoretically have all the same endgame potential as AonDor and/or Forgery.

The Allomancer that dies from Heavy Metal Poisoning for not burning off their metals before bed. Anyone that Stores Gold To Death.

Hoid: Kashmir by Led Zeppelin

damnation, my mistake. I knew it was the specific exception in that did not source the power in Preservation, but I thought there was still a conduit to the Spiritual Realm at play, just with a different destination.

To add to what @Extesian said, they dont have enough energy left in their Spiritweb to get much of a charge from them, but it's a matter of quantity not quality, all the needed pieces of the process are there. You'd have better luck spiking traits back into a Lifeless than getting them out I think. Either way though, I dont think you can spike out a Lifeless's lack of need for food and water. That's not a spiritweb trait, that's a base function of being animated by a Breath rather than Food and Life, and you cannot spike out non-Divine Breath.

No, even with godmetals the burned metal is still creating conduit to the Shard's infinite store of energy in the Spiritual Realm. The Compounding hack is all about plugging that Allomantic power Conduit into the feruchemical side of the systems, so if your spiritweb has the ability to do Feruchemcial stuff with that Godmetal and also can create the allomantic Conduit with it, the trick still works. The biggest qualitative difference is that in the case of Atium the conduit goes to Ruin rather than defaulting to Preservation. It is worth noting that it does not work right out of the box with any godmetal, they have to be "Plugged In" to Scadrial and the Metallic Arts sufficiently for their metal to have both an Allomantic and Feruchemical function.

Yup, though it sounds like it has more to do with the Seon's Bond to their master than anything else

That's an RAFO so far. We know that Sazed is still blind to metal, but we dont know if all shards are innately, or if other shards would be on Scadrial.

It could go either way, I think all the groundwork is already there in the case of the Elantrians specifically, who are already Bonding a spren/Seon directly; they might be able to figure out something themselves with the proper motivation, though seeing the Rosharan example would certainly help them along. I do not think they would manifest the Surges unless they were actually ON Roshar, or were actively trying to mimic them. I think they'd be manifesting their own Symbol-based Dor Abilities rather than Surges, Ideals, etc. but I fully expect they could make Shardblade equivalents at least as well as Awakening, and likely more so since Seons are a lot closer to Spren than Breaths.

The biggest functional difference is that Forgery is an ongoing effect that needs to be maintained and can be disrupted, whereas Soulcasting triggers a permanent change and leaves no active Investiture behind. Among other things, it's the reason you can create Aluminum via Soulcasting but not Forgery.

Whats more, the surges are part of Roshar itself the way Metals are natural to Scadrial. Which means a Selish equivalent would be manifesting entirely different things than the Surges; if instead they are juicing Dor "Reality programming" effects up to Rosharan power levels, that could be just plain cheaty.

I had the opportunity to listen to the Graphic Audio of Warbreaker recently (HIGHLY recommend them, if you have the chance, the full cast and production is a wonderful experience), and I noticed something about Lightsong that stood out but was never really addressed: Lightsong is unwholesomely Lucky. At one point Lightsong is playing a game called Tarachin with the other Gods, a game described as "one of the most difficult games in the world" because it required both great physical ability as well as layered strategy. Lightsong, being awesome, never bothered to learn the rules and instead just likes to choose and throw the balls randomly, yet he always manages to do better than the avid players. So there he is, musing about how the different Gods get slightly different forms, how they all seem to get more or less the same Godlike physique but unfortunately there's no guarantee of any increased intelligence. Meanwhile he's throwing balls over his shoulder and winning at a game he doesnt understand all the while wishing he knew enough to be able to loose on purpose. Here's the thing, we know that the Returned's physical attributes get way more Fluid, reflecting more of what they Believe they should be rather than their inborn reality (and this can be consciously manipulated with training). Most got Young and Huge and Physically Impressive, at least one got Old and Wise because she believed in that godly image. But Lightsong never really believed in his own Divinity, and I think that deep down he believed that all the Returned were just People Who Got Lucky. In light of his performance on the Tarachin Field, I think Lightsong was actually Augmenting his Fortune attribute. And if Returned are indeed influencing their spiritual Attributes as well as physical, there's every possibility that they could learn to consciously manipulate those attributes the same way Vasher (or the Royal locks line) can willfully control the physical portions of their Spirit-web. Given how the Breaths work by sort of merging with (or overlaying on) the Spiritweb, it would make logical sense that it would be positioned to subtly manipulate it, and Breaths respond to Intent/Commands directly more than a lot of Investiture types.

As @Agent34 said, AonDor is effectively the ability to reprogram the Universe via Cognitive constructs (ie Symbols). It (and Selish magics in general) are some of the most versitile and powerful magics we've seen, with their two drawbacks being that you have to KNOW the right symbols, and also that Selish magics are fundamentally tied to Physical location and homeland. The same way Hemalurgy can do a hell of a lot if you know the secrets, you have to know the right symbols to be able translate effects from different "programming languages", and fortunately there exists a Rosetta Stone to help translate the effects (potentially even translate other magics system effects). With that the AeonDor should be able to mimic just about ANY cosmere effect, and given the extreme versatility of Forgery, that's some amazingly diverse options. From a very Doylistic perspective, I think the Selish Magics are going to prove to be some of the most Powerful and diverse in the Cosmere endgame, with that power balanced against its location limitations. If Scadrial is going to be the race of very physical spacefaring science, Sel will be the home of the true Wizards (Elantrians=elves, methinks) that are busy hacking reality itself. Scadrial is the Physical focus poster-child, Sel is the Cognitive, and Roshar is the Spiritual; this follows with their Investiture and I think will be the central thrust of their endgame roles as well.

That would be a reasonable description of a solid object's behavior, but since it would pure Investiture Id think it should be sufficient to block a shardblade, at least to Half-shard levels. Since even full shardplate cannot hold up against a Blade indefinitely, Id think they'd still be able to hammer through this eventually, but where it would land between shardplate and half-shards I couldnt say without testing. Separately, since Seons are supposed to basically be the Sel equivalent of Spren, I kinda hope to see one attempt their own Nahel bond and manifest a Seon Blade and Plate.

Int he case of Slivers, holding any significant portion of Investiture warps the Spiritweb of the Holder such that when it is released there remains permanent stretching, which causes weird effects. It does not have to be that you held literally all of a Shard (since Rashek never actually took a shard from Leras or Ati) but you do hold enough Investiture to cause the warping.

I think it is establishing that shardblades can indeed damage manifest Spren in the Physical Realm. This is something that likely didnt come up as much with the previous Radiants where the sides were more clear, but now that we're likely going to see more actual bonded Radiants and/or Voidbinders on Odium's side, ones that will be able to manifest spren as actual living shardblades, it's likely there will be more spren-on-spren violence.

Harry Potter and the Sorcerers Stone