StanLemon

I don't think they will fall out of relevance, just that the list of options will expand. But that expansion will be affected or even bounded by the magic systems you have.

Considering Wax's perception in BoM and Kelsier's in TLM, it seems that Steelsight could look into into the Spiritual Aspect of a Spike with a tweak

I'm not sure how that reads to you, but based off the context of the conversation, that reads like "plug themselves into the Spiritual Realm to power their Invested Art"

I think you may have misunderstood the original comment. Quantus seems to be talking about drawing power directly from the Spiritual Realm, not going into it.

Technically every time they burn metal

Considering how quickly breakthroughs have happened in the real world (car to landingon the moon in less than a century), most of those are reasonable in only a century or two. South Scadrial already has the technology to make machines use Allomancy for example. They already have the seeds to what they need. Also, Scadrial has much more reason to invest in space travel than we do. Space development continued advancing and making breakthroughs while we were still funding it but then as a society space travel stopped having the appeal. Partly because we hit the walls of real world physics limitations, but also it became harder for countries to justify the spending on further developments. Take Space-X for example, many of the developments they have done were theorized decades ago, but actual money and engineering were put into it. I agree that it would take decades to develop colonization and research outposts, but if they create an FTL drive in only a century after Era 2, they could have all that by two hundred years post Era 2. YatNP shows that Investiture is a very good means of propulsion considering the society personally visited another planet in their solar system at a tech level at best comparable to ours.

I think you are vastly underestimatin how much Allomancy and Feruchemy would ease space travel. One of the hardest parts of space travel is just gravity. Iron will be immensely useful for that. Food, water, air storage? Cadmium and Bendalloy. Heat buildup? Brass. Calculations done with Zinc. FTL made possible with time bubbles. Many of the hurdles we have with space travel are things the Metallic Arts already have answers for, or at least have aspects that simplify the problems.

That's in part because we are heavily restricted by real world physics. Scadrial has numerous powers that are exceptionally useful for making space travel much more viable. So I could see Scadrial being space age in just one or two hundred years, especially considering they rebounded from near societal collapse and advanced to turn of the 20th century development in only a handful of centuries.

Considering that there was a network of interplanetary trade as early as TFE, it's quite reasonable that at least an early form of them existed during that time

Reading through this chain I have a few comments. First, Steelpushing and Ironpulling make monumentally more sense if you think of them as applying an identical force on the metal and Allomancer. It's only because of Newton's third law does the lighter object move, not some intrinsic aspect of heavier vs lighter objects. A good example of this is when not-Wax Duralumin fueled Pushes off a car and the car is flattened from the force of the Steelpush while he's launched into the air. If it was just his weight vs the car he could never flatten it like that , but it makes a lot more sense if the care suddenly had an incredible force applied to it and nowhere to go. I think there is plenty more we don't know about how Pushing/Pulling work but it does seem the more power put into it the less counterbalance of weight matters. Secondly, we see near Vin Ascension levels when Wax uses the Bands. He Pushes a boulder off of him by the trace metals in it. And then proceeds to use a Steelpush that smashed through a stone wall

The Sunlit Man seems to have given given us an explanation why Breath from children is considered better than from older people. The Investiture thresholds are similar in concept to Heightenings. According to Sigzil as long as he retains certain levels he gains abilities, and while those abilities do use Investiture, it's only a tiny amount. Applying this logic over to Breaths and Heightenings, the benefits of Breath, even just one very slowly use up the Breath. This difference between a young and old Breath is probably small enough that it doesn't make much of a difference between dozens or maybe even hundreds of Breaths, but on the scale of 10s of thousands it like Susebron, it could make enough of a difference to explain why they get their Breaths from children for the Returned.

So a while back on one of the Fullborn vs Radiant threads there was a lot of talk about mass and density and how F-Iron doesn't make sense. I threw out an equation off the cuff about how to ro rectify this m=(p x V) x I m - mass p - density V - volume I - Investiture There were a few issues with this as it was a quickly put together equation. But one of the arguments was that it implies Investiture changes mass and things like Nightblood were brought up that it isn't super heavy etc. However this book does straight up say that high levels of Investiture seemingly does alter mass. Or at least acts as additional mass on spacetime. A line from the book also caught my attention The part I found interesting, which admittedly could be reading too much into the wording, is the implication that even though it has this mass like property it doesn't affect density. This could explain some of the F-Iron weirdness in that the Investiture for Iron Feruchemy could be going toward just this property of Investiture thus explaining the mass/density contradiction partially. There are other issues but it could be a start

I trust that Brandon will make future Scadrial more nuanced. Especially because a) Sigzil's comment about Scadrian factions and b ) the final series in the Cosmere will be Mistborn series but it sure feels like he's presenting them as the "bad guys"

Except the Shroud stops existing at the end of the book. It's like saying a Returned who has used their Divine Breath is still being kept alive by that Divine Breath that doesn't exist anymore. All Cognitive Shadows we know of need something to hold their physical bodies. There Heralds need the Oathpact, Kelsier needs his Spike, the Returned need Divine Breath. Yumi doesn't have that limitation With the Shroud dissipating at the end, it's not there to hold her physical body. I agree with you that her regrowing a body isn't any different than Investiture healing, but I think it's fair to say she's not a Cognitive Shadow anymore and truly came back to life

I'm assuming she's a flesh and blood human again. All the other Cognitive Shadows we know of need some kind of "tether" to have physical bodies like Kelsier's Spike, The Oathpact, Divine Breath, etc. There's nothing like that even hinted at to be the case at the end of the book

Here is a thought, maybe it's related to how younger Breaths are better than older Breaths. It could be linked to the life force of the user

Ah, my apologies then. The last time I had read that page, the part about the newest edition retconning that hadn't been in the Coppermind.

That's exactly what I'm saying, none did. During that conversation Elend thinks to himself about the standard Spikes an Inquisitor has and is surprised that there is an extra Spike in that specific Inquisitor. And he's surprised when it's Pewter. It wasn't until the reveal that it is a Pewter Spike that they even start thinking that it's a third power from Allomancy and Feruchemy because he starts thinking about how Allomancy and Feruchemy use different metals for different effects. None of Elend's line of thinking makes any sense if any of the Inquisitors in Kredik Shaw had any Spikes other than Steel or Bronze

He couldn't have had F-Gold for one very simple reason. The only Spikes that Vin or Elend had seen from any Inquisitors before HoA were Steel and Bronze. This means Kar could not have had Feruchemy

I'm personally a fan of A-Bendalloy and F-Steel as a Twinborn combo

Considering Inquisitor's are described as aging slowly and living longer, Spikes do no cause faster aging. It's more likely that those that 'burn up' are simply overtaxing their bodies like someone who does too much labor breaks down their body. Also, though it might be an effect of Pewter Allomancy boosted by Hemalurgy, Kar the Inquisitor that Vin harmed and was fully healed by the time she next saw him only hours later could not have had Feruchemical Gold so he clearly had a higher healing rate than a normal person rather than a reduced rate

There's the character named 16 in Rhythm of War

I very much would love more A-Gold in the books. Your reference to Everything, Everywhere, All at Once is how I often have viewed how it could be used. In fact a few years ago me and my group played a MAG where we let A-Gold be rolled for that exact effect giving Traits for my character. My inspiration for that though was from Emperor's Soul and the use of Soul Stamping. An alternative life you could have lived with skills you could have developed.

Brandon has made a comment that Steel/Iron burn quickly but Allomancers generally don't notice because they aren't Pushing all the time. This implies to me that burning it for the blue lines is slow but burns faster when actually Pushing/Pulling. This would be in line with his comment about burn rate being tied to how much work the Investiture is doing. As to your second question. Weight matters, but it isn't the determining factor for strength of Pushes/Pulls exactly. Think of the blue line as a force acting equally on both the Allomancer and the metal. When a Coinshot Pushes, the force is Pushing against the Allomancer and metal identically. Per Newton's 3rd law, any action has an equal and opposite reaction. This leads to a greater amount of net force being applied to the lighter object which then moves away from the heavier object. As far as your third question goes, I personally think that it doesn't require burning any more Steel or Iron. The greater mass of the metal seems to naturally translate to thicker blue lines that can be seen at greater distances. In effect a Coinshot would be Pushing harder off of it, but that's more of a consequence of the greater net force acting on the Coinshot

Additionally he has said they are more flexible than the medallions