Nemesis, Cowl, and the Circle

There is no Black Council. It's a hypothetical construct created by Harry to explain the connections he saw between his casefiles. Nemesis is what Harry calls the Black Council. Harry wasn't cleared to know about Nemesis when he joined Ebenezar's Grey Council, so Ebenezar utilized Harry's Black Council to explain it to Harry without revealing Nemesis to him.

There is a Circle, even if it is only a circle of Cowl's minions. But I posit that the Circle is an organization of self-aware Nemesis agents.

Operation Starborn was a Circle plot. We have Lord Raith involved in that operation, who is clearly connected to the Outsiders. We can also speculate that Arianna Ortega is part of Operation Starborn, given her presence at the dinner party. Maggie tried to recruit her father, and failed. She may have recruited another White Council wizard. (I suspect Cristos!)

Maggie, realizing that Nemesis was behind the Operation, fled the Circle and cut a deal with the Leanansidhe, an agent of the Grey Council.

What?

The Grey Council is the group Neuro calls Team UMO. We know that Vaderrung is an ally of the only known Grey Council agent, Ebenezar (unless I've misinterpreted the climactic battle at Chichen Itza in Changes), so I'll default to the canonical "Grey Council" over UMO. The Leanansidhe works for Mab. Ebenezar works with Vaderrung.

Cowl, I suspect, is Cristos. Arianna is Kumori.

Old Nick's contingent within the Knights of the Coin are also opposed to the Outsiders, but not members of the Grey Council.

It's pretty clear by now that the Outsiders are the big villain of the series, from Harry's origin story with He Who Walks Behind to the Big Apocalyptic Trilogy. Nemesis as the Black Council is the glue that holds the Outsiders in the main antagonist plot.

1. The Shadowman, given the Heart Asplode spell from a Nemesis agent. This spell is similar to the Familicide spell in Changes.
2. The Hexenwolves, given belts by a Nemesis agent.
3. Cowl and Kumori, Nemesis agents, appear onstage.
4. Aurora, either corrupted by Nemesis or driven insane by knowledge of Nemesis.
5. Nicodemus actively working against Nemesis.
6. Lord Raith.
7. Cowl and Kumori.
8. Maeve, corrupted by the Leanansidhe, manipulating Eldest Fetch, Lily, and Harry.
9. Lord Raith versus Cowl.
10. Nicodemus again with a diabolical plan to stop Nemesis.
11. Peabody, a Nemesis agent.
12. The Lords of Outer Night, agitated by Arianna Ortega, a Nemesis agent among their ranks.
13. The Fomor, who probably worship the Outsiders (to go along with the Lovecraft homages) appear onstage.
14. Maeve.
15. Nic. He is just the worst.

Jotunheim is Arctis Tor

ABSTRACT
TL;DR

The divide between the Faerie Courts coincided with the Fae assuming the defense of the Outer Gates, and also with the decline of paganism in Scandinavia. Previously, the Jotun had guarded the Outer Gates, and the Aesir had protected Midgard from the Jotun. However, with the decline of pagan worship, Odin, the Normans' chief god struck a deal with the Fairy Queens¹, the Celts' chief goddesses, to ensure the defense of Reality.

The Creation of the Fairy Court

Hecate

Per Bob, Hecate was originally a Hag who achieved divinity through a bloody ascension rite.² Mythologically, she's one of those weird pre-Olympian mystery goddesses infesting Greco-Roman paganism. The tri-part goddess statues in Hades' Vault³ lead us to conclude that the three Fairy Queen mantles are, together, Hecate in her triple goddess form (Mother, Maiden, Crone). Given the confusion in the real world over whether Hecate is the Crone or the trinity, I'd say it's fair to assume that she is both. At some point after her ascension, she spun off her power into the three mantles, and kept the Crone mantle for herself.

It is currently unknown to whom Hecate the Crone gave the other two mantles to, and I know I've shed pixels trying to pick Olympian divinities who could take the mantles. This makes no sense, however, as the Olympians have their own divinity, and would not need to accept more power from Hecate the Crone. Given the connection apparent between Hecate and the Fae, we must look elsewhere in Europe.

The Tuatha De Danann

The Tuatha De Danann are the predecessors to the Fairy Court. The Leanansidhe characterizes them thus when describing their enemy, the Fomor.⁴ Mythologically, they are the Celtic pantheon, but Christianity sapped their power, spinning them into heroes with supernatural powers instead of gods. I speculate that the Crone Hecate found her Mother and Maiden within this pantheon of not-quite divine figures. By binding the Mother, Maiden, Crone to the existing Tuatha De Danann, the Fairy Court arose from the Mantle-wearers and their followers.

The Defense of the Outer Gates

There exists a feud in mythology every bit as petty and deep as the feud between Winter and Summer. I am speaking of course, of the feud between the Aesir and the Jotun. I predict that, before the Fairy Court split, the Jotuns guarded reality from the Outsiders. There are easy parallels to make between the Frost Giants and the Winter Court, but two stood out to me:

1. Both have wells. Underneath the World Tree, according to the Eddas, on the path to Jotunheim, sits the Well of Mimir. It seems likely to me that this corresponds to the Winter Wellspring.

2. Jotunheim, of course, was on the edges of Ginnungagap, the primordial void from which reality was made. Winter, of course, finds itself on the edge of Reality at the Outer Gates.

It seems to me that the case can be made that Arctis Tor is built atop old Jotunheim, and that the Outer Gates were at one point defended by the Jotun. This would slot the Aesir into Summer's role, protecting Reality from the Jotun.

1066 - The Battle of Hastings

1066 is where this all comes together. The Norse Normans invade Celtic England even as Norse paganism is on the decline, and Christianity on the rise, in Scandinavia. The decline of paganism is a problem for the Aesir, as they aren't worshiped as much as in the past, and are losing power. This is not a problem for the Jotun, as they aren't worshiped as such in the first place. The invasion of England is a problem for the Fairy Court, as the people who tell their stories are getting slaughtered.

So Odin, chief god of the Normans, and the Fairy Queens, representatives of the English, meet to discuss terms. This is a blending of the various sources for British fantasy, the Norse, Celtic, and Greco-Roman religions. The end result is that the Jotun are banished (to team up with the Fomor), the Normans take England, and the Fairy Court splits to assume the defense of the Outer Gates. Hecate the Crone assumes the Mother Winter role. And she loses her walking stick.

Mab and Titania

My gut says that Mab was the Maiden at the time of the split. Then, during the split, the Crone Hecate became Mother Winter, The Maiden Mab promoted herself to Winter Queen, and the Mother became Summer Queen. For symmetry, Mab's twin sister, Titania, became the Summer Lady (where Mab started). When Mother Summer abdicated (I'm still going to guess this was Baba Yaga), the Summer Queen became Mother Summer, and Titania became Summer Queen.

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1. To distinguish the pre-division Court from the Summer and Winter courts, I will use Fairy Mother, Queen, Lady, Knight, and Court to describe the pre-division Court.

2. Welcome to the Jungle.

3. Skin Game.

4. Ghost Story.

There's nothing magic about it, and maybe nothing conscious on Harry's part (then again, does Harry ever consciously Name someone?), but I think it does, in fact, matter.

Don't know of coins can change genders, so I think Thomas and Eb are safe.

... Huh? Lasciel is identified as female and we spend five books watching her try to get Harry to partner with her.