Found this WOJ quote on Reddit

Looks like according to this WOJ the Erlking is a member of the Winter Court, I guess like Vadderrung is a member of the Winter Court in his Kris Kringle carnation... He is also referred to as the "Master of the Hunt"  or Herne and was called by that name in one of the books.

Yes, Erlking "hangs" with Winter more than Summer.

But he's more "Summery" in himself...

Jim: He is wyldfae.  He isn’t a subject of Mab or Titania.  That’s what Wyldfae means.  But his origins are in the Summer-side of the cycle of seasons, just like Titania’s are.
Ditto Santa, only in Winter

I think the problem is with us in the fandom:  we want to try to assign categories for these beings, and they just don't fit neatly into the boxes we have... nor neatly and entirely out of our boxes...

... It's also possible that his publisher just has so much in the pipeline that next January is the first open slot they had.

This is my suspicion.
Also, we all may be hoist on the petard of Jim's slower & less-predictable pace:  publishing lead-times have only increased, with the supply-chain problems that occur these days, and their queue likely filled with other works while Jim was chanting a mantra of, "it'll be done when it's done."

Amazon often uses placeholder dates. I suspect this is one. 

That was my thought, too.

Sadly, it looks like the info is accurate:
https://www.penguinrandomhouse.com/books/645506/twelve-months-by-jim-butcher/

https://www.amazon.ca/dp/0593199332/ref=monarch_sidesheet_title

Of course they say so, but it seems in Ghost Story/Changes Mab has some power over the cold and dark of the deeps...

Well, to be fair:
 a/ "cold" and "dark" are pretty Queen-of-Winter sorts of things, after all!
 b/ that scene at the end of Changes was the culmination of Mab's gambit to gain her new Knight.  I expect she handled it personally... and likely she had some of her other heavy hitters on-hand in case any other powers wanted to intervene.
 c/ we've seen that Demonreach has scope as far as the edges of the lake.

So, as Harry was aboard the Water Beetle, considering his upcoming date with Murphy:  Mab (and likely other Winter heavyweights) were there, and maybe even Demonreach.

And I don't think the Fomor had any motivation to be active at that specific harbor, on that specific day; I don't think they (and/or their allies) were tracking Harry very closely, at that point in time.


I don't think she has the kind of sovereignty under water that she has above.  One of her titles is "Queen of Air and Darkness," which pretty explicitly leaves out the underwater realm.  But she's still terribly-powerful, and entirely capable of conducting a brief mission outside the strict "Winter" domain, particularly in (winter-friendly) "cold and dark."

But... does she have the kind of power needed for sustained surveillance under the water, with Corb & the other Fomor against her, and even Ethniu?  To spot patterns?  Does she know all the underseas Ways?  Did she even want to go (or (previously) see reason to go) sniffing into the areas where the Fomor were forced, millenia ago?  I suspect the  answer to all is, "no."

So yeah:  Mab, moving in power & with backup on-hand, opposed by maybe (but probably not even) a random scout, or whatever?  Sure, that happened & makes sense...  Without it implying Mab having any her usual one-step-ahead (or several srwps, for that matter) foresightedness.

... So I suspect the Fomor have the home field advantage, but various powers did know SOMETHING was up with the Fomor. They just didn't know what...

In addition to their "home field advantage" under water, the Fomor had another advantage:  everyone already knew they were "making a move."  They were taking advantage of the power-vacuum and WC weakness &c to make a bid to become more active in the world.

So troop-movements &c might be "expected" from them.

But a direct challenge to all the Accorded powers at once?  Making a simultaneous power-play against Mab and Odin and Ferrovax??!?

Who TF does that?

It was in the general discussion in Dead Beat regarding the EK.

I think he's "Wild Fae" in the sense of "not technically owing allegiance to either Summer or Winter Courts.  The Erlking is his own sovereign monarch.

.... And it was explicitly stated in Battle Ground (during the discussion with EK and Vadderrung before the big fighting starts that EK is Winter Fae.

That's the bit where I need to track the exact language, and context; they might have just been talking about field-command and battle arrays, not overall mystic politics.

Similarly for the opening night of _Peace Talks_, before Ethniu arrives:  was Erl there at the talks?  Did he have his own separate "contingent," or was he attached  to Mab's group?

When did that happen.  In Dead Beat he was “Wild Fae”.  Did something change or did Mr. Butcher change his mind? 

Where is that passage?
I'd have to re-read it.  Off the top of my head, though:  I might suspect it was just a battle-order sort of thing, allowing for Mab to have ultimate field-command of all Fae forces.

...  That’s one of the things he originally sacrificed his eye to gain… access… to knowledge actively concealed.

Yes; but the "Norse Pantheon" has no particular supremacy over any others; and thus Odin might be supreme in his hidden-knowledge vs. other Norse deities, he wouldn't have the same advantage vs. the Celtic pantheon (from which Ethniu derives).

Fundamentally, though:  Ethniu always was allied with the Fomor.  Balor (her father, whose Eye she carried as a weapon) was one of the war-leaders of the Fomor.

… but complete tactical and strategic surprise?  It’s very difficult to believe that old one eye had no idea the Fomor Peace Conference was a complete ruise ...

This is a reasonable question.  Large-scale military movements "should" not be hard to detect... OTOH, we're not dealing with a RL army & RL logistics:  I'm sure they could stage a huge army in their heartlands, then open a Way down on the lakebed, and march (swim) in thousands per hour...

I also go back to the "undersea" thing.  I'm unclear how much Odin's power extends down there; offhand, I recall no Norse lore saying he had any adventures or conquests there.  In the Norse myth-cycles, the "Vanir" were a peer/rival group to the Aesir with whom they eventually made peace; it was the Vanir king Njord who was the "Lord of the Oceans and Winds."

And similarly, the Fomor were associated with the underseas.

So their foreignness (combined with undersea supremacy) might have been enough to keep the secret even from Odin.