Hypothesis: The Nightwatcher is not actually the Old Magic

[Juanaton]

I’m not confident enough in this to call it a theory, but I do think there is some significant support for the idea I just had.

The Vorins consider the Old Magic and Nightwatcher to be synonymous and blasphemous. Since we know the humans on Roshar originated elsewhere (Ashyn), I believe the Old Magic actually refers to the magic of Ashyn. Since that magic (boon) is granted by sickness (curse), it makes sense that the Nightwatcher’s activities would come to be associated with that, particularly after enough time had passed for the Rosharan humans had forgotten their other worldly origins, but would still have vague myths and legends about how the Old Magic operated and it matched up with the Nightwatchers boon/curse game.

Now if this is true, it MIGHT imply that ALL magic from Roshar is surgebinding, all magic from Braize is voidbinding, and all magic from Ashyn is the Old Magic...in other words, the shardic source of the investiture doesn’t determine the magic, the planet of origin does.

[Calderis]

18 minutes ago, Juanaton said:

The Vorins consider the Old Magic and Nightwatcher to be synonymous and blasphemous. Since we know the humans on Roshar originated elsewhere (Ashyn), I believe the Old Magic actually refers to the magic of Ashyn. Since that magic (boon) is granted by sickness (curse), it makes sense that the Nightwatcher’s activities would come to be associated with that, particularly after enough time had passed for the Rosharan humans had forgotten their other worldly origins, but would still have vague myths and legends about how the Old Magic operated and it matched up with the Nightwatchers boon/curse game.

This I see as very plausible. It lines up very closely with some ideas that @Vortaan has brought up with about magic available during the initial desolations that I agree with.

18 minutes ago, Juanaton said:

Now if this is true, it MIGHT imply that ALL magic from Roshar is surgebinding, all magic from Braize is voidbinding, and all magic from Ashyn is the Old Magic...in other words, the shardic source of the investiture doesn’t determine the magic, the planet of origin does.

This part I don't agree with. Brandon has spoken if three magic systems on Roshar. 

Quote

Questioner

How many magic systems are in The Stormlight Archive, and how many of them haven't been seen?

Brandon Sanderson

I would say the only major one you haven’t seen is Voidbinding, it depends on how you count them.  I count fabrials as one, Surgebinding as one, and Voidbinding as one.  And then the Old Magic is kind of its own weird thing.

source

Considering we've been told of the magic of Ashyn as something different, I don't think those categories would be applied by planet.

Edit: one of the things that Vort brought up is that in the Elia Stelle it mentions the humans having surges... Which should be referring to a time prior to the desolations. 

The Heralds were made as an effort to contain the Fused, and the Nahel bond was made in mimicry of the Honorblades... So where would those surges mentioned have come from, unless the diseases of Ashyn were brought with them.

I definitely think that may be the origin of the term "the old magic" 

Edited August 1, 2018 by Calderis

[Wyndlerunner]

I always just read "Old Magic" as magic that predated the modern Surgebinding (Note I use the term modern very loosely, as in most definitions, Surgebinding would not be a "modern" or recent development.)

[galendo]

On 8/1/2018 at 4:15 PM, Juanaton said:

Now if this is true, it MIGHT imply that ALL magic from Roshar is surgebinding, all magic from Braize is voidbinding, and all magic from Ashyn is the Old Magic...in other words, the shardic source of the investiture doesn’t determine the magic, the planet of origin does.

Possible but it would set Roshar apart from the only other example Cosmere example we have of a planet with multiple active Shards -- Scadrial -- where there are at least two separate magic systems, despite the planet of origin being the same.

Mistborn spoilers:

Spoiler

Allomancy, Feruchemy, and Hemalurgy all seem like multiple systems that work different ways, with the only real common ground between them being that they all use metal.  Now maybe you could argue that there really isn't that much difference between Allomancy and Feruchemy, but IMHO Hemalurgy is pretty clearly its own separate thing.  Not so much for the whole "stealing powers" thing, but because nothing in Allomancy or Feruchemy would allow for Steel Inquisitors to live with spikes through their heads without the constant use of magic.  That should have been very noticeable if it were happening, so we can safely assume it isn't.

[Ripheus23]

I think the Old Magic might be the leftover magic system of Adonalsium himself, from his creation of Roshar. This involved the spren, so when Cultivation came to overshadow the spren ecology, her powers became affiliated with the prior order of Adonalsium as such.

I think the Ryshadium might be related to this state of affairs, too. If they have bonded with musicspren, they might be the equivalent of "Knights Radiant" for Adonalsium himself (maybe there's even an implicit relationship between the words Adonalsium and Ryshadium).

EDIT: I can't believe I said "boned with musicspren." Now if THAT isn't a terrible image... 

Edited August 8, 2018 by Ripheus23