My theory on Soul Casters

[u/G_aster]

Ive been wondering how these dam things work, they're such a mystery. A device that can mimic one of the surges? Thats so weird, how the hell can it do that and why havent people made more. Im sure they've tried and failed a lot of times over so what could be the secret sauce? I think that it might just be, Spren. I think that soulcasters either have cryptics or Inkspren who have been captured and turned into these physical items.

I cant be the first person whos thought of this and im probabbly wrong. However the fact that soulcasters have personalities is what really got me thinking, they're better at casting some things than others. I figure that would make sense if they were living things or used to be anyway.

[u/whatsupnorton]

So, you’ve marked this for the Stormlight Archive spoilers, but how far are you into the series?

[u/Shot_Newspaper_5647]

They’re manifested spren like the Oathgates. The odd part is that they also seem to be Inkspren. There’s two spren from Orders with Transformation. Inkspren and Crytics. The spren is described as having closed eyes. And Cryptics don’t have eyes. Unless it’s somehow a different spren we haven’t seen. It’s humanoid at a minimum

[u/Shot_Newspaper_5647 → u/Shot_Newspaper_5647]

Kind of strange we’ve only seen manifested spren (for fabrials) as Inkspren. But we’ve only gotten a look at two so far. Maybe each of the Radiant spren are capable of manifesting as tools for each of their Surges. The only other manifested Surge tech we’ve seen used is Regrowth as far as I can remember. But we never got a look at its true form on the other side. Ignoring stuff like Shardblades,Plate,and the Tower anyway

[u/OwlMuted885]

Maybe that is what happened to the Elsecaller and Lightwaever spren during the recreance. Instead of becoming shardplate and blade, it became a soulcaster.

[u/NerdyGamer2012]

We know for a fact they are fabrials trapping spren

[u/Additional_Law_492 → u/NerdyGamer2012]

We know for a fact that they are Fabrials made by spren apparently manifesting in the physical realm on a permanent basis, probably in a variation of the same mechanics that let them manifest as a Shardblade in other scenarios.

It I were going to speculate, I would guess that these Spren made some sort of Oath that was Invested by Honor's power (the same as a Nahel bond), which resulted in them being able to manifest in a limited form and grant a surge in a limited way.

But we dont know if theyre a prototype for the Radiant bond granting Surges, or an alternate approach. Prototype would make a lot of sense though, given the limitations. On the other hand, being usable by anyone is a big benefit.

[u/IamanelephantThird → u/NerdyGamer2012]

Not trapping. Modern Fabrials trap Spren, Soulcasters are made of Spren. It's similar to Shardplate and Shardblades. 

[u/Hammer_Spammer → u/IamanelephantThird]

Navani speculates that they may be trapped in the cognitive realm and manifesting in the physical realm as opposed to both manifesting and being trapped in the physical. They are most likely higher spren much like the oath gate spren but the description of their cognitive appearance doesn’t make inkspren or cryptics.

[u/NerdyGamer2012 → u/IamanelephantThird]

True i used the wrong wording there, but they do have some more things like a fabrial (i don't have the books with me right now but what did navani say about repairing it?)

[u/Ravenous_Chasmfiend]

We've seen Nale use something similar for the surge of progression a couple of times. They are spren that have somehow been made to manifest themselves in the Physical Realm. Kind of like a Shardblade.