I think the big difference between the nightmare meal and a mantle is when you consume another spirit it becomes part of yourself, you can get tainted or mad if you consume the wrong spirit.
A Mantle is a way to reduce that risk by keeping the extra power as a seperate entity. We see that some people are better than others in seperating themselves from their mantles but they all do otherwise they end up crazy like Lilly.
I think the memories are stored both in the spirit and the soul and that is how Harry could be rebuild after he lost most of his spiritual essence. Most spirits are without soul but I think beings like Harry are not entirely unknown. Corpstaker was one and Kemmler must have been one several times. It is the only way a necromancer can return from the dead.
The deads in a darkhallow would be usefull for the wizard performing it in several ways, not the least because it frees their spirits to be consumed with the rest of the ghosts.
The problem lies, for me, in drawing the line at what is and isn't a Mantle, and whether a Mantle can be an non-sentient being in and of itself. For example, we know that the Winter Knight mantle grants power, abilities, and knowledge. According to WoJ, the bearer can influence the Mantle to some degree. Countless homicidal WK's have probably added to the pre-existing darkness that would accompany a Mantle of Winter.
How does that influence occur? Well, in the Dresdenverse, we have at least one example of people swapping bits of their souls with each other when they're close (Harry and Karrin). We've also got an example of a free willed person changing an eternal being (Harry and Lash).
Maybe it's not too far off to guess that some sort of soul exists within a Mantle itself. Maybe not the poetic, pretty version of a soul that we're used to. But maybe the technical, Dresdenverse soul that is a collection of memories, experience, knowledge, and self.
There's a WoJ, I believe, talking about how Molly has a soul still, but will slowly lose it if she remains WL. And he also says that Mab had a soul at one point, but he's not sure how much is left. In the Dresdenverse, things aren't given for free. The bearer of the Mantle gets a lot from the Mantle, and has to give something in return. What if it's their soul?
I don't mean in a soul-eating way, or a eternal damnation sell-your-soul way. I mean, what if the Mantle is some sort of non-sentient lifeform, which absorbs the soul of the Mantle bearer over time? It would explain a lot; as the bearer takes more and more of the Mantle personality onto themselves, they lose that much of themselves.
My interpretation of that would not be that the Mantle itself is malicious, or trying to do harm to the bearer. It's just existing. And the soul wouldn't be devoured or consumed and then disgarded. It would become part of the collective Mantle.
My only fear in this is that it might support the crazy Mab=Molly theory subcategory, "Molly will be Mab, as Mab is every other Mab before her."
In that sense, a Darkhallow ceremony would
have to absorb both (
of my theoretical) soul and spirit of those killed in the process. In doing so, it would merge all of that soul and spirit energy into a new, non-sentient entity, which would be bonded with the bearer like any other Mantle. Then, if and when the bearer dies, the Mantle would continue to exist, and another could take it up, thus trading (unknowingly) their soul for power.
The obvious argument against that is smaller Mantles, like the Santa mantle. There's been theories banded about regarding Odin, and whether or not he's the "first" Odin, or just the current bearer of the Mantle of "Odin". If he bears an Odin Mantle, then the conflict arises when there are two Mantles associated with one soul; who gets what?
This post is so full of awesome, especially the section analyzing differences between soul and spirit and body under the Darkhallow heading.
I have 2 comments to make.
We have another example of spirit consumption when Corpses Taker ate all the mad spirits near the end of GS.
Also, I have some interesting takes on how the soul works. They are partially shaped by something Lea said to Harry while he was recounting his fight with HHWB
This conversation immediately made me think of some of Harry's experiences with Lash/Lasciel. She made some similar comments about Harry's mortality limiting his perceptions on things, and notibly also had access to perfect recollection of things Harry had experienced. Also remember how Bob said that angelic types are pretty much all soul and nothing else. So either the eternal soul is these memories, or has a facility that can access them perfectly. When I was reading Dead Beat, I always thought Lash was picking/using Harry's wetware (brain) for the photographic memories she was able to recall, but after reading GS it seemed that as an angelic being she was able to view Harry's soul directly and pick the information from that.
Good point about the Corpsetaker instance. In that scene, she absorbed the spirits to herself, thus boosting her power. Since the spirits wouldn't be anything truly pure in memory, they might not influence her.
Part of me wonders if that might also explain the body-swap process: the spirit and body remain, but the souls are swapped. With Luccio's soul in a new body, with a weaker and different magical spirit, she isn't able to do the same things she was able to do before. For Corpsetaker, she jumped without a spirit (or much of one, at any rate) and body to attach to, so she ended up drifting as a soul. With the consumption of all of those spirits, it gave her 2/3 of the recipe.
As for Lash, her being pure soul makes partial sense to me, but I think she was only a
part of the Lasciel soul-entity. Lasciel probably took a piece of her own abundant soul energy, containing a snapshot of her knowledge and power, and slapped it onto Harry's soul and body. Once there, it should have worked on Harry, until he eventually took up the coin, and the soul fragment returned to the whole. Then, as I speculated above with the Mantles, Lasciel might give power and knowledge to the bearer, in return for their soul being devoured. In this instance, it would likely be more like consumption/absorption with mal-intent, since Lasciel perceives herself as a greater being that had to bow to lesser beings.
But when Harry sealed away the coin, Lash didn't have a clear connection back to the whole Lasciel entity. So she fed off of Harry's soul, very minutely, in a manner similar to Harry and Karrin swapping bits. Enough that they influenced each other; Harry, with his quick temper while hosting Lash, and Lash becoming more understanding and open to change.
Lash, being primarily a copy of a soul-entity, would likely have access to Harry's pure soul memories. It would explain her perfect recall of things he'd seen and done. But I think she also had knowledge that he was unaware of. In the garage in PG, she basically ran sonar for him, despite the fact he couldn't draw on magic. She wasn't pulling 100% from memory, because it was real time. So I think the soul-memory thing explains most of it, but not all.