Why do Returned need investiture to stay alive?

[Calderis]

2 minutes ago, navahgar said:

Calderis, how do we know that that other type of Cognitive Shadow we've seen doesn't have the requirement?  Is that confirmed anywhere?  Roshar is a great source of Investiture, as we know specifically in this context from a certain worldhopper's presence there.  Maybe all Cognitive Shadows in physical bodies do need a constant supply of investiture.

We're in the Cosmere theories thread so we don't need to worry about spoilers. There have been multiple threads on this topic recently so I was confused on what forum we were in, and what had already been posted here. And on that note

http://www.theoryland.com/intvmain.php?i=1048#4

Quote

RYBAL

Can the Heralds Surgebind without their Blades and if not are they under the same restrictions that others are?

BRANDON SANDERSON

The Heralds without their Blades are incapable of the powers you're familiar with. It doesn't mean there aren't other things they can do.

Without the Honorblades, the Heralds have lost their surgebinding based abilities. Thus they aren't able to invest Stormlight. Other than Nale, they've gone 4500 Rosharan years without that ability so they don't seem to need it. 

I know Vasher having other abilities seems to counter this, but Vasher has a wealth of knowledge that the Heralds simply don't. He worldhopper before Nightblood's creation, and interacted with a group of others who had done the same. 

The Heralds are bound to the Rosharan system and spent their time between desolations being tortured. They didn't have time to study the rules of the Cosmere like Vasher did. If they have a requirement, they figured out a way to obtain Stormlight through other means in an unbelievably fast timeframe after giving up their Honorblades, with no apparent casualties to even learn it was needed in the first place. 

[navahgar]

Thanks for the clarification.  According to that WoB, the Heralds without their Blades are incapable of the powers we're familiar with, but that doesn't mean they're incapable of absorbing Investiture from stormlight to feed their Cognitive Shadow needs.  So I'm not sure that WoB closes the issue.  I think it's feasible that being on Roshar inherently feeds the Investiture needs of the Heralds without any them needing to be smart enough to figure it out.  Vasher may have had to be smart to hack into it, but the Heralds were created in this system, so I don't see any reason for them to need to have studied the rules of the Cosmere to make it work.  Having said that, I see your point and I guess we'll have to wait and see.

On a slightly tangential note, that WoB looks a bit sneaky/complicated to me.  The question was can Heralds Surgebind.  The answer was that they are incapable of the powers we're familiar with.  So is that a no then?  Sounds to me like he purposely avoided directly answering the question.  

[Calderis]

2 minutes ago, navahgar said:

On a slightly tangential note, that WoB looks a bit sneaky/complicated to me.  The question was can Heralds Surgebind.  The answer was that they are incapable of the powers we're familiar with.  So is that a no then?  Sounds to me like he purposely avoided directly answering the question.  

Well I think we've already seen it. 

Taln catching a dart midair that he could barely have seen coming seems to be fairly super human. And that is after separation from the Honorblade. 

[navahgar]

Just now, Calderis said:

Well I think we've already seen it. 

Taln catching a dart midair that he could barely have seen coming seems to be fairly super human. And that is after separation from the Honorblade. 

Yeah.  That was a really interesting scene.  I had a theory about that, that the Taln we see in that scene is a kandra (with a spike enabling feruchemy/allomancy for speed), and not actually Taln.  The real Taln having been switched out between the end of WoK and that part in WoR.  This could explain the whole 'the person calling himself Taln' narrative.  This theory seems pretty bad though, since others pointed out (on reddit) that it would be too big a crossover of Cosmere into Stormlight, and I think there was a WoB that explained his logic behind the Taln confusion was a holdover from a previous draft.

Assuming my theory is wrong.  Those quick reflexes could derive from some of those other inherent powers that Heralds have.

[+Extesian]

I should say, as the OP, that I'm not satisfied that Heralds didn't have a way to draw in Stormlight, just like Vasher did. And they certainly would have had the knowledge to use gems and such to see them through the highstorms. My theory, at least the specific idea that only Returned amongst Cognitive Shadows need constant investiture, depends on it. But I haven't satisfied myself yet that Heralds are any different. Even if they are, they haven't been described as exactly Cognitive Shadows, Brandon has described them as 'technically a variety of Cognitive Shadow'. We have Kelsier of course but we've still only seen him in the Cognitive Realm where investiture requirements may be different (ie the idea that it is the physical body and the connection to it that needs maintaining). Kelsier did become one because the amount of investiture he took in 'expanded his soul' to the point it no longer felt the call of the Beyond. That clearly indicates that the Cognitive Aspect itself does not need a constant flow of investiture. Once it's expanded, the pull of the Beyond stops. So the question remains, is it the physical body that causes that need.

[Brightlord M. Alhstrom]

On 7/28/2017 at 2:12 PM, Calderis said:

He worldhopper before Nightblood's creation, and interacted with a group of others who had done the same. 

Can I have a WoB or other canon source backing that? And if so, could he be storing stormlight in gems and bringing it around with him to replace the breath a week requirement of his Returned status?

[The One Who Connects]

16 minutes ago, Lord Maelstrom said:

Can I have a WoB or other canon source backing that? And if so, could he be storing stormlight in gems and bringing it around with him to replace the breath a week requirement of his Returned status?

Have a few entries from Pagerunner's List. Not sure about the "group of others," but...

Quote

Q: Can Nightblood be considered a splinter and does it function like a spren realmatically, are there distinct differences is what I'm asking.
 
A: Nightblood is kind of his own strange thing. He's an attempt to use one magic to replicate something in another. He's closest to a spren, but kind of like a...robot spren, for lack of better words to use.
 
Q: When you say that Nightblood is "an attempt to use one magic to replicate something in another," do you mean life in general, or are you referring to a specific effect in a specific magic system?
 
A: There are those involved who knew that Shardblades existed before they tried the Nightblood experiment.

Q: So does this mean Vasher had knowledge of shardblades before creating Nightblood?
 
A: It means what I wrote, and nothing more at this point.

Quote

Q: You said before that nightblood was modeled after shardblades intentionally so my question is, did vasher created his Phantoms with shardplate in mind?
 
A: He was aware of Shardplate, but I wouldn't call them a conscious influence.
 
Q: Any sort of influence from the Soulcasting-to-Stone burial customs?
 
A: Let's say that yes, soulcasting was very interesting to Vasher.

And as for your idea, the only thing that would stop him would be not being able to draw it out of gems like the KR. Otherwise, yea he could do that.

[Calderis]

The "group of others" I was referring to was the other four scholars. 

I highly doubt Vasher alone worldhopped in that group. 

[The One Who Connects]

54 minutes ago, Calderis said:

The "group of others" I was referring to was the other four scholars. 

I highly doubt Vasher alone worldhopped in that group. 

Oh. Yea that makes sense now. Vasher certainly did, we have confirmation about Denth  and Shashara, but I don't think we have anything about the other 2.

Quote

Q: Has Vasher ever been to a world other than Nalthis or Roshar, or was this his first time worldhopping?
 
A: Vasher has only been to Roshar and Nalthis, beyond places in Shadesmar.

Quote

UESTION

Has Denth ever been to Scadrial?

BRANDON SANDERSON

So Scadrial is one of the planets that’s easier to get to, in Cosmere terms. I will say this: he did not travel the Cosmere widely. But Scadrial is one of the easier ones to get to - he spent a lot of time on Roshar, and did not travel widely

Quote

QUESTION

So, Vasher, and maybe some of the other ones have been off world--

BRANDON SANDERSON

Shashara has been, yeah.

[Aether]

Ok. Flexing my muscles a bit here. 'Tis been a long time, so bear with me as I might not be completely up to speed, nor will I remember all my sources, but there is a few things I'd like to point out. Do point out if and when I get something wrong.

On 28.7.2017 at 3:08 AM, Extesian said:

On Elantrians, we know they are not Cognitive Shadows as they never ‘died’. I did a post on this a while back, I believe the mechanics are that they are normal magic users, but infused with investiture to the point of effectively coming savants (many caveats on that due to the rubbery definition of savant). As Calderis said, I think the appropriate analogy is to someone with the fifth heightening who is not a Returned (ie susebron rather than vasher). I think you and Maelstrom have it right, that basically when Elantrians use aons they are not actually channeling the investiture through their bodies in the way an allomancer does when burning metal. The super boost caused by the Elantris aon (when functioning) is designed to enhance their ability to pull more of the Dor in at once, but it seems like the kinetic investiture is not actually running through them. Either way though, as they’re not cognitive shadows, the point is somewhat moot.

On the issue of why one Breath a week (technically it’s the eighth day  they die) that’s exactly part of why I think this is a very deliberate choice by Endowment. If they needed investiture constantly, in small trickles, the first Returned would have died immediately. It needed to be a week to give them time to convince others to give Breath. The number of days could be a Nalthis number thing, but I think it’s more just a good balance of not too short and not too long, as hwiles said, it’s a motivating factor to give away the Breath eventually.

In the end I’m pretty confident that the design of all of this is about creating an ecosystem of ‘giving’ on Nalthis. The main question I haven’t satisfied myself with is whether that’s the only reason why Returned need regular investiture, or whether all Cognitive Shadows do and Endowment’s Intent is simply what defines the specifics.

I do think you guys are onto something here. The Returned's vampiric tendencies is likely heavily tied to Endowment as a shard more so than to the more general workings of the Realmatics behind Cognitive Shadows. Some others have pointed out that there is one major difference between Returned and (most) other Cognitive Shadows that we've seen, and that is that they are the only ones who've got their own physical bodies, so there is still room for their Investiture Drain to be more of a general thing rather than a quirk of Endowment, but we have too small of a sample pool to answer this in any definite way, IMO.

We have seen at least two - possibly three - other examples of cognitive shadows stitched to a physical body, and that is that of Kelsier from BotM, the Heralds and possibly Szeth. Kelsier (or whatever is going on there) is likely stitched to a body by Hemalurgy - and Hemalurgy comes with its own pile of weird interactions and rules, so nothing definite from that example. The Heralds seem to be something of a whole other calibre than even Returned, and even if not, there is likely a bunch of rules and stipulations that come from the Oathpact, so Heralds know how that is supposed to work (pardon the awkward and terrible pun).

On 28.7.2017 at 10:12 PM, Calderis said:

Without the Honorblades, the Heralds have lost their surgebinding based abilities. Thus they aren't able to invest Stormlight. Other than Nale, they've gone 4500 Rosharan years without that ability so they don't seem to need it. 

This is likely just plain wrong. Just because they do not have their Surgebinding abilities without their Honourblades does not mean that they cannot use or wield Investiture - even if they do not have a direct "funnel" for using Stormlight specifically. There are jailbreaks to the different forms of Investiture - plenty of WoBs that confirm that. The mere presence of Vasher on Roshar confirms this, so I'm not going to bother hunting those WoBs down.

Point is, Brandon has hinted at the Heralds having other abilities, and the way he's worded it in the past seem to imply more than just super-human levels of strength, dexterity and such. I find it likely that they have powers that require Investiture, and given their strong bond with Honour (at least in the past), they can probably wield Stormlight directly. And if not, there are ways to get around that, as previously stated.

Also, just because we haven't seem them use these powers during the few relatively short interactions we've had with them in the books, doesn't mean that they do not have them or cannot currently use them.

On 28.7.2017 at 10:12 PM, Calderis said:

The Heralds are bound to the Rosharan system and spent their time between desolations being tortured. They didn't have time to study the rules of the Cosmere like Vasher did. If they have a requirement, they figured out a way to obtain Stormlight through other means in an unbelievably fast timeframe after giving up their Honorblades, with no apparent casualties to even learn it was needed in the first place. 

We have no idea how old the Heralds are and how long the conflict on Roshar has been in play. Even if they wouldn't have had time to study during the Desolation, that does by necessity mean that they haven't had time to study it before. And they seem to have known Tanavast personally (either from before his ascension or in the beginning of his godhood), so who knows what they may or may not have been told directly.

On 28.7.2017 at 10:23 PM, Calderis said:

Well I think we've already seen it. 

Taln catching a dart midair that he could barely have seen coming seems to be fairly super human. And that is after separation from the Honorblade. 

That might not require use of Investiture directly, though. Consider the Elantrians and anyone holding a lot of Investiture (Stormlight in particular), really. Super-charged human abilities is likely just an off-shoot of being a heavily invested being, either by having much more of it as a part of your very being (such as with the Elantrians) or by holding it temporarily (such as with anyone holding Breaths or Stormlight or channeling the Dor with your fists as that weird Kong-Fu trader did in Elantris).

On 6.8.2017 at 0:42 AM, FiveLate said:

I am not sure I can agree with this completely.  Yes the Heralds were created through the Oathpact with Honor, but that might not have been in the Rosharan system of magic.

Do we have direct confirmation of the Heralds being created as a part of the Oathpact? And even if so, does that mean that they were created as sentient beings at that very moment or that they were just elevated to demi-gods from "normal" humans at that point?

We seem to be in agreement about the point your trying to make, but I think you have reasoning wrong, here.

 

Edited August 7, 2017 by Aether
Orthography

[Aether]

And as a general note on Nightblood: It is not that he kills you unless he gets the proper fuel, its that he need the proper fuel or he will turn you into the proper fuel.

Remember that Investiture is literally small pockets of the power of creation. EVERYTHING has Investiture, in a way, but much of it isn't in its raw form. When Nightblood doesn't have any easily-accessible fuel at-the-ready, he turns you into that fuel by breaking you down into Investiture and then feeds on that.

 

I am reasonably certain that I am correct on this point. I'll try to see if I can hunt down the correct WoBs if I get the time tomorrow.

[Calderis]

@Aether true I'm making assumptions that I shouldn't be. 

When Navani and Dalinar (and Renarin) are discussing the desolationa after one of his visions in tWoK, he asks "but what were they" and Navani with something along the lines of "wars, terrible wars. A continuation of the fighting that pushed mankind - and the Heralds - out of the tranquiline halls" (emphasis mine) 

So if the mythos of the tranquiline halls is indeed based off of migration from another planet, it's very likely they have access to another means of investment and my earlier assumptions are invalid. 

7 minutes ago, Aether said:

And as a general note on Nightblood: It is not that he kills you unless he gets the proper fuel, its that he need the proper fuel or he will turn you into the proper fuel.

Remember that Investiture is literally small pockets of the power of creation. EVERYTHING has Investiture, in a way, but much of it isn't in its raw form. When Nightblood doesn't have any easily-accessible fuel at-the-ready, he turns you into that fuel by breaking you down into Investiture and then feeds on that.

 

I am reasonably certain that I am correct on this point. I'll try to see if I can hunt down the correct WoBs if I get the time tomorrow.

There are multiple WoBs that says that Nightblood will feed on any investiture including the "spark of life."

He doesn't bother changing you into fuel, he just consumes the pattern of you that already is. 

Edited August 7, 2017 by Calderis

[Nathrangking]

I believe that Nightblood consumes the soul in lieu of breath... when necessary. The soul as has been shown is in fact made up of investiture which as a last resort is used as a power source.

[Aether]

1 minute ago, Calderis said:

There are multiple WoBs that says that Nightblood will feed on any investiture including the "spark of life."

He doesn't bother changing you into fuel, he just consumes the pattern of you that already is. 

We seem to be in agreement on this point, though we express it differently. Whether Nightblood "transforms you into fuel" or just omnomnoms you directly is really just silly semantics. Point is that everything is creation and that Investiture is the power of creation and whether it is the one the other both or whatever he eats, he will eat away at you nontheless.

The point I was trying to get across (or at least the one I originally wanted to make but lost somewhere in the process of a long post), was that I do not feel the fact the WoB someone quoted earlier in the Thread, that the Elantrians probably shouldn't hold Nightblood unless they found a way to power it with the Dor, means that the Elantrians aren't full of Investiture (as in being in a state where they are permanently holding in the Selish equivalent of Stormlight and that Nightblood would feed of that first and THEN kill them if that was the case). Elantrians are full of Investiture, the way I see it, but it has become a part of their being rather than just holding it in permanently (imagine someone finding a way to just permanently hold in a stormload of Stormlight, without really using it up). So feeding of their excess Investiture, as compared to normal humans, would kill them just as feeding of the inherent Investiture of normal humans would kill them.

Or at least that is the way I have come to interpret current data. Point is, everything is creation, and Nightblood omnomnoms creation (though he seems to prioritise the raw form), and I believe we agree on that latter point, at least.

[Aether]

6 minutes ago, Nathrangking said:

I believe that Nightblood consumes the soul in lieu of breath... when necessary. The soul as has been shown is in fact made up of investiture which as a last resort is used as a power source.

Yes. You said in two sentences what I used... more... to try to express

I would add that he consumes buildings too. Because "everything is creation", to quote myself.

[Steeldancer]

I'm going to make a little theorization, based on the model of realmatics I just posted a topic about. 

So the returneds soul has been stapled back to the body with investiture. Now imagine it like this: a balloon in the realms. That is the soul. It wants to leave to the beyond, and is constantly trying to push away. The investiture is like piling a weight onto the balloon to hold it down. (Just accept it. I know normally the balloon would just pop, but this is a metaphor). But, the balloon pushes some of the weight off, (consuming the breath) and unless you pile more weight on it, it will eventually float away into the beyond. 

[Calderis]

@Aether I agree in part. I don't think Nightblood can feed on anything. 

Brandon has stated repeatedly that while we have energy and matter, the Cosmere adds a third layer to this in investiture. 

Nightblood only seems to feed on investiture. The one time we do see him unseated and using his immense capabilities for destruction, he does seem to completely obliterate matter into investiture upon striking it, and I'm sure he would consume it then, but the cost/gain ratio seems like there would be far more lost in the conversion process between states than he could sustain. 

The spirit web is already composed of raw investiture, so I agree, if he runs out of a held source, be it breath, Stormlight, an actively burned metal, or whatever else, he will move on to the soul. I don't believe he would be able to feed beyond the soul and start consuming the physical body though. The cost/gain ratio would just be too high. 

In the case of an Elantrian I also agree with what your saying. They have been invested, and it manifests in their physical appearance. An Elantrian wielding Nightblood would need a way to connect him to the Dor to wield him safely because otherwise Nightblood would immediately turn on them. The problem here is that with the investiture having become fully a part of them, he would still be eating into there admittedly more invested souls. So it would take him slightly longer to fully consume them, that isn't necessary to cause irreparable damage. If he were to eat a small section of their soul it would most likely still be fatal, in the same way that Hemalurgy doesn't take a large portion. In that same line, just as Brandon has said that if someone does manage to survive being spiked, they would be something akin to a drab, and their personality would most likely be drastically altered, surviving a partial feeding by Nightblood would probably be... Unpleasant. 

[Aether]

2 minutes ago, Flash said:

So the returneds soul has been stapled back to the body with investiture. Now imagine it like this: a balloon in the realms. That is the soul. It wants to leave to the beyond, and is constantly trying to push away. The investiture is like piling a weight onto the balloon to hold it down. (Just accept it. I know normally the balloon would just pop, but this is a metaphor). But, the balloon pushes some of the weight off, (consuming the breath) and unless you pile more weight on it, it will eventually float away into the beyond. 

Although the metaphor is... weird... I think you might be on to something here. However the mechanism actually functions, a soul needs something to avoid ascending (descending? Moving laterally?) into the Beyond. The big question is what the difference between Returned and other Cognitive Shadows (physically stapled or not) constitutes.

Given our lack of information, what makes the most sense to me thus far is that this is either a quirk of Endowment, or a necessity of anchoring the Cognitive Shadow to a physical host. I would prefer to stop at that and toss a "Dunno, let's RAFO" at it until we get more information.

2 minutes ago, Calderis said:

@Aether I agree in part. I don't think Nightblood can feed on anything. 

Brandon has stated repeatedly that while we have energy and matter, the Cosmere adds a third layer to this in investiture. 

Nightblood only seems to feed on investiture. The one time we do see him unseated and using his immense capabilities for destruction, he does seem to completely obliterate matter into investiture upon striking it, and I'm sure he would consume it then, but the cost/gain ratio seems like there would be far more lost in the conversion process between states than he could sustain. 

The spirit web is already composed of raw investiture, so I agree, if he runs out of a held source, be it breath, Stormlight, an actively burned metal, or whatever else, he will move on to the soul. I don't believe he would be able to feed beyond the soul and start consuming the physical body though. The cost/gain ratio would just be too high. 

In the case of an Elantrian I also agree with what your saying. They have been invested, and it manifests in their physical appearance. An Elantrian wielding Nightblood would need a way to connect him to the Dor to wield him safely because otherwise Nightblood would immediately turn on them. The problem here is that with the investiture having become fully a part of them, he would still be eating into there admittedly more invested souls. So it would take him slightly longer to fully consume them, that isn't necessary to cause irreparable damage. If he were to eat a small section of their soul it would most likely still be fatal, in the same way that Hemalurgy doesn't take a large portion. In that same line, just as Brandon has said that if someone does manage to survive being spiked, they would be something akin to a drab, and their personality would most likely be drastically altered, surviving a partial feeding by Nightblood would probably be... Unpleasant. 

Feed might be the wrong word to use, and I might have fallen into the trap of having my understanding of this being influenced by my own poor choice of words.

The way the Nightblood is described in Warbreaker certainly has a "feeding" feel to it, but it might be that he just destroys everything around him in a prioritised order as long as he is being wielded. As above, let's throw a "dunno" at this and await further info.

And about that cost/gain, ratio, I remember a WoB where it was stated that Nightblood actively destroys Investiture to a certain extent. I'm trying to track it down, but my Theoryland skills are rusty. (Have they gotten the new WoB search engine up and running, yet?)

[Calderis]

10 minutes ago, Aether said:

I'm trying to track it down, but my Theoryland skills are rusty. (Have they gotten the new WoB search engine up and running, yet?)

I've gotten better with it, but theoryland is... Something. 

It's supposed to be up shortly before the Oathbringer release. I can't wait. 

As for Nightblood he definitely feeds on investiture. 

http://www.theoryland.com/intvmain.php?i=1093#5

Quote

PHANTOMMONSTROSITY

Let's say some mistborn jerk tosses Nightblood into the mists. What happens?

BRANDON SANDERSON

I suspect the mists would pull away from Nightblood, though he'd try to feed on them.

And there's another that says he's "removing" investiture from the Cosmere but it's been debated heavily. I think he only "removes" it through corrupting it into a non-usable state. 

And my Theoryland skills aren't good enough to find what I want... Blah.

Edit: to clarify, I don think investiture can be "removed." 

It can be converted between the three states, and corrupted into a state that it not accessible, but it like matter and energy cannot just simply cease. 

Edited August 7, 2017 by Calderis

[Aether]

I stopped looking for new quotes after having tracked down... quite a few... Putting them in spoiler tags in order to not have a mile-high post:

Spoiler

Quote

Fletchershair
Now that Nightblood is on Roshar, can it feed off of Stormlight the same way it can off of Breaths?

Brandon Sanderson (Paraphrased)
(...) Yes. Nightblood will feed on pretty much anything.

<source>

Quote

Question
How does Nightblood work on Roshar?

Brandon Sanderson
Well, Nightblood feeds on Investiture, which is the general life-force/magic-force in the Cosmere and so he can feed on basically any source of magical energy.

<source>

Quote

Leinton
Does Nightblood possibly rip souls out of people?

Brandon Sanderson
Nightblood consumes Investiture, including the spark of life.

<source>

Quote

Question
How much more powerful is Nightblood than a regular Shardblade?

Brandon Sanderson
I haven't actually quantified that in my own mind, so can't give an accurate comparison at this point. I will say that when he is fully consuming Investiture he can do some really freaky things.

<source>

The general gist of these (and more, these are just some of the examples I found) are two things:

• "Feed" doesn't seem to be something I have just started using myself, as Brandon constantly uses the word himself. In fact, he literally consumes the Investiture, so saying he just breaks things down isn't quite correct.
• That last one seems to imply that we haven't seen Nightblood being used to its (his?) full potential yet, and that it (he?) has only been partially using most of the Investiture he seem to drain from his surroundings. What this means for the loss-ratio when he (it?) is being used to his (its?) full potential, I have no idea.

I do not know if Nightblood needs to destroy Investiture in order to work, but these WoBs (and other) seem to imply that the Investiture loss as the sword has thus far been used, at least, is quite heavy and that much of it is just... gone.

EDIT:

26 minutes ago, Calderis said:

It can be converted between the three states, and corrupted into a state that it not accessible, but it like matter and energy cannot just simply cease. 

I don't know. The general feel that I get from a lot of WoBs about Nightblood is that there is at least some form of loss, but your interpretation here is effectively the same thing anyway, so, yet again, "I dunno".

Edited August 7, 2017 by Aether
Answer to previous poster's edit

[Fatling]

9 hours ago, Aether said:

I do not know if Nightblood needs to destroy Investiture in order to work, but these WoBs (and other) seem to imply that the Investiture loss as the sword has thus far been used, at least, is quite heavy and that much of it is just... gone.

EDIT:

I don't know. The general feel that I get from a lot of WoBs about Nightblood is that there is at least some form of loss, but your interpretation here is effectively the same thing anyway, so, yet again, "I dunno".

Maybe Nightblood takes investiture to be evil, so consuming investiture is how he fulfills his original charge to "destroy evil". If that were the case then he would indeed need to destroy it.

9 hours ago, Calderis said:

And there's another that says he's "removing" investiture from the Cosmere but it's been debated heavily. I think he only "removes" it through corrupting it into a non-usable state. 

And yeah I would agree that Nightblood is destroying investiture by breaking it down so it isn't investiture any more... though I don't know what it would be after it has been broken down. It seems like Nightblood has a turns matter into creepy smoke. Near the end of chapter 56 of Warbreaker:

Quote

Vasher screamed, charging toward the side of the room. He slammed Nightblood through a wall. The stone dissolved just as easily as flesh had, evaporating away before him. He burst through the dissipating black smoke, entering the next room. He didn’t bother with a stairwell. He simply jumped onto a table and rammed Nightblood into the ceiling.

A circle ten feet wide vanished. Dark, mistlike smoke fell around him like streaks of paint.

Maybe investiture is transformed into the nasty liquid mentioned in the same chapter:

Quote

He ran forward and grabbed Nightblood’s hilt and pulled the sword free, leaving the sheath behind in the body.

The blade sprayed a wave of black liquid as he swung it. The liquid dissolved into smoke before touching walls or floor, like water in an oven. Smoke twisted, some rising from the blade, some falling in a stream to the floor, dripping like black blood.

Sorry, I just realized that's kind of a lot of quote boxes