[Spoiler] Isn't Dark Knight using Akasa ?

[Veloran]

The Mistborn analogy doesn't apply well here. The central problem is 'main villain is immortal, nobody can defeat him.' When the resolution to that conflict is 'The protagonist was secretly more powerful than she realized', then there never was a conflict to begin with. It doesn't really matter when you introduce that fact. Deus Ex Machina eliminates the central conflict by sidestepping it. Sanderson's point about having a 'victory condition' is important. He contrasts Helm's Deep and Pelennor Fields in that the solution to both problems is similar (big army shows up, we win), but one has a foreshadowed victory condition (survive for five days) and the other does not. Without that victory condition, there is no dramatic tension, because you can just win at any point that you feel like. You can, however, distract the audience from that condition, which is why its to your advantage to introduce the rules of the game earlier rather than later.

But all of that does apply to Dynamis? All of the pieces are only set on the table in the final 90% of the story, and then are only moved into position in the final zone, equivalent to like the last page of the book. In terms of "victory condition", Dynamis is like if Aragorn was getting ready to charge out of the hall at the end of Helm's Deep when a bird flies in through the window with a note saying "you've survived five days of suffering, the Elves could never have done this, look to the East!" It's an element introduced at the very end that provides both the impetus and resolution to the central conflict. Beforehand we could not have even guessed that this would be the central conflict because neither Meteion nor Dynamis had been revealed to the audience.

The main conflict is an ideological one. Stand up to Meteion, and show her your will to live.

But it isn't an ideological conflict, not strictly speaking. The conflict, indeed the entire history of the world up until this point, revolves around the physical capability to utilize Dynamis. Simply showing Meteion a will to live means nothing because she is perfectly willing to suffocate such a will with her overwhelming power. And that overwhelming power can only be counteracted with Dynamis. The main conflict is that the villain is undefeatable without this deus ex machina entered into the plot in the final moments of the story.

When you have limited information to go on, you have to be careful not to infer more than you actually can.

The issue here is that we are being asked to look in on critical plot elements, character motivations, and decisions/actions that exist, effectively, within a void of knowledge. As Sanderson notes, a magic's integration into the story is reliant on how well the reader understands it. As it is we don't understand it at all, and neither do the characters in the story, so a very large part of the narrative is reliant on the reader not thinking critically about something that we have very limited information about.

I'm sure that we'll learn more as we go. For one, there is a lot about Void Magic and the Voidsent that we still yet don't know, and this is probably the one thing that I'm the most curious about. I wouldn't be surprised if we get a referential tie in here somewhere, especially given that Diabolos was the creator of Dynamis in FFXI.

This is currently the most interesting aspect of Dynamis to me as well, as it could potentially explain various things about the Voidsent or why the Void reads as having no aether despite clearly containing matter and energy. To clarify, the reason why I have no issue with this is because the Void and Voidsent are mostly unexplained or at least have some clear contradictory workings at the moment, while numerous other elements (certain jobs, Omega situation, LBs, etc) already had various other explanations that were at least as sufficiently explained as being one type of energy versus a new one. That, and unlike the Void many of these other elements were already thought to be well understood beforehand, in the sense that characters had recognized them to be aetherical in nature. The Void, however, has much more mystery to it and therefore more room for new explanations.

[Lauront]

This is currently the most interesting aspect of Dynamis to me as well, as it could potentially explain various things about the Voidsent or why the Void reads as having no aether despite clearly containing matter and energy. To clarify, the reason why I have no issue with this is because the Void and Voidsent are mostly unexplained or at least have some clear contradictory workings at the moment, while numerous other elements (certain jobs, Omega situation, LBs, etc) already had various other explanations that were at least as sufficiently explained as being one type of energy versus a new one. That, and unlike the Void many of these other elements were already thought to be well understood beforehand, in the sense that characters had recognized them to be aetherical in nature. The Void, however, has much more mystery to it and therefore more room for new explanations.

I share your reservations about how Dynamis was utilised ultimately. I don't have a problem with the idea, as such, as there has long been a suggestion that souls have something irreducible about them that can survive even aetheric destruction - albeit not the corruption wrought by the latest version of the Final Days. Moreover, prayer and the like as a component of primal summoning has long been a thing. I'd just like to see what the writers do with it when less pressed by time and without a giant legacy plot to address in such a short timespan. My impression of it is that it isn't so much antithetical to aether (in the sense of one cancelling out the other - it's more of aether being like a buffer) but that its comparative subtlety makes it harder to notice and thus manipulate if you're dense in aether, as aether can negate it by virtue of a buffer effect. Elsewhere, you've mentioned some potential workarounds the ancients had to this (even if by proxy methods, e.g. familiars) and it would be interesting for that to be explored in the future. Oddly enough, it appears to be so elusive that in spite of all the stars she encountered, Meteion is surprised by seeing it manipulated. Whether that is because you hail from Etheirys, or because it is just that elusive, is unclear. Even in Ultima Thule, the beings you interact with readily understand the concept of aether but I only recall the Ea mentioning dynamis and even then, being impressed by the application of it, so it suggests even for exceedingly long-lived civilisations, it is something of a mystery.

As to the Void, it's an interesting case as there's both things militating for and against it. We know the Void ultimately fell due to auracites being rather bad at bottling up a primal, and eventually an ensuing flood of darkness. Knowing now that the rites the Ascians taught the beast tribes are not quite the same as their own creation magicks, the requirement that a primal constantly feed on aether may be unique to those, so I do wonder if a lot of the higher order Voidsent that we see are in fact primals, whether in the usual or the bodysuit sense. Assuming the measurement tools used to track the movement of aether are not up to the task at measuring dark aether, and the world is saturated in dark aether, they could feed off that. Darkness is a highly energetic form of aether, so a world saturated in it and primals fed from it could simply be highly potent as a consequence.

On the other hand, Primals are formed of a mixture of incorporeal and corporeal aether, as well as prayer (willpower etc. also suffice), the latter of which is hinted to tie into dynamis as well as supplying the incorporeal aether. Yotsuyu struggled to sustain her primal form until she managed to tap into that wellspring of hatred inside her. This may mean Primals may end up being capable of hybrid energy consumption, if one knows how to utilise the construct to wield both energy sources infused into it (sort of like Elidibus seemed to do if we take the LB surges to be dynamis), and irrespective of how the two energies would interact in a regular mortal being. If we say that dark aether becomes a little boring as your sole source of nourishment for thousands of years (and this will apply across the board as all living creatures apparently require nourishment to replenish their corporeal aether), it is understandable why you'd want something purer and more varied, be it aether or otherwise. A primal may have a further recourse (even if it does not realise it consciously) and begin drawing on dynamis. Alternatively, if the world is bereft of aether, then dynamis becomes an alternative power source in its own right. It is also of note that Voidsent hunger for aether and, for some, their victim being in a state of terror or despair can improve the pleasure they derive from it. The workings of it are vague, but they’ll even devour each other for power, as is known from both Dun Scaith and the reaper quests. So to me there’s an either/or here, because the workings of both Voidsent (beyond being the dark and more wilful mirror to Sin Eaters) and Primals are not fully laid out. We simply know that there are ways to mirror their creation, via the tank role quest in SHB, involving stimulation of the subject's aether.

One thing that muddles matters is that magic consists in being able to manipulate one's corporeal aether (Garlean inability to use it is ascribed to a general inability to do this), and so it is logical that emotional states might force it one way or another, and interact with aether to produce darkness, with or without dynamis. Dynamis as I recall it is weaker but more prevalent than aether, as well as prone to surges. The Mhachi were using Voidsent to do things like power the Void Ark (didn’t end well, of course, but because Scatthach was so powerful and they lacked proper means to control her.) So for the time being I would hesitate to tie everything back to dynamis just because it involves emotions or force of will, although it would be feasible to write it in such a way if one chose to. With the Void they do have a lot of leeway and a story arc to continue from SHB with Beq Lugg.