As I have theorised it is actually more likely that he is able to undertake a sanctum invocation with a nascent genius loci of Chicago.

If there is a genius loci of Chicago, Namshiel could have given Marcone a substantial lead over Harry towards recognizing its existence and bonding with it - provided Namshiel doesn't fear making the host too powerful, in their relationship, anyway.

Bonding with a genius loci would go a long way towards explaining why Marcone was able to manifest his own Banner in BG, though.  Harry's was as a function of the Knight mantle.  I don't see why being a Denarian would grant Marcone the same, but being bonded to the spirit of the city would make for a stronger case.

That's not to say Harry might not be Marcone's successor to it at some point, but if you're right about such a genius loci existing, I suspect it's already spoken for at this point.

I don't see Wizard of Chicago as a mantle. Why should only Chicago get one? Where is his domain? Marcone's lands? Demonreach is the White council's  prison, not Harry's.

I don't think Demonreach is the White Council's, actually. Just because Merlin made it doesn't mean they've kept up continuous control over it. They failed to prevent one of their worst enemies, Kemmler, from becoming one of the more recent Wardens, and they basically view any of their members taking up the Warden mantle with actual knowledge of what they're doing as tantamount to an act of rebellion and declaration of war on the Council.

Basically the few of them who are aware of Demonreach at all want it kept dormant.  It's not much of a claim.  Now that they've kicked Harry out, announcing himself as Warden is probably his best claim to being an independent power. Now, is that a good idea? Probably not - it would draw the attention of any nasties who haven't already realized he's the Warden.

Cite, please?
I know it as a popular fantheory, but I know of no "canon" or WoJ on the topic.

There's a WOJ that there is an upper limit on the number of beings it can control at once. Which makes sense, because if it could just spread without limit and infect all the (non-starborn) mortal population, it probably already would have won that way.

It's fan theory that the number of the cap is 13, though.

They're pathologically averse to cluing in mortals to act as 'the help', and pathologically arrogant about the value anyone but a wizard could contribute. And they use junior wizards as receptionists because one thing very rich and powerful old people really love to do is enforce their juniors 'paying their dues' - even if those juniors are capable wizards themselves.

That hasn't killed them *yet* because 1) they're insulated by fantastic amounts of money and magical power, and 2) most of the rivals in their ecosystem are equally, if not more, averse to moving with the times. Most of the other hidebound nations have a blind spot that the way the Council is doing some of these things even is a weakness at all.

But some of their antagonists who aren't so set in their ways.  Lara, for one, has basically referred to the Council as a dead organization in the long term that happens to be still walking around in the short term.  Splitting Harry off and tying an alliance to him is basically salvaging an asset before the shipwreck - it's just that a lot of things move very slowly among the nigh-immortals.

The reason the Council are still alive isn't because the world is badly written, but because they're falling from a great height in slow motion. It's been foreshadowed that they're on track to either end or go through a transformative reorganization, though.

Kumori was interested in Necromancy because she thought it could heal death, this is another point for Sarissa

I don't discount the possibility, but I'm not convinced it's the only one, either.

For one, if we're open to Kumori being someone Cowl revived by necromancy ... what about Aurora?  Interest in healing, check. Delusional and already connected to Nemesis, check and check.  Would cause Harry pain to face again, check. And there have been a relatively limited number of antagonists who tried to convince Harry to go along with their plans or stand aside because they believe they're doing the right thing, rather than threaten or bribe him off a case - Kumori and Aurora were two of those.

Not sure I actually believe that theory, but she does tick a lot of boxes.

It's unfortunate that Harry didn't recover the memory of those minutes he lost after the curse went off while his memories were no longer limited by meat storage during Ghost Story.

On the other hand, spending a few months screaming wouldn't have been conducive to being the fulcrum for Molly and Mort to stop Corpsetaker, so maybe not after all.

So it's actually not Michael, but Father Forthill who reveals this information.

Also, while Anduriel can hear and sometimes see out of any shadow, he can't do this out of every shadow. I highly doubt he can do it on consecrated ground like that of a church, given how hard it is for spiritual entities to even get onto church ground. Talk about a threshold.

....

I don't mind the Kim Delaney theory. Definitely has some merit. What's Kim's connection to Cowl though? And why Kim over Harry (the strongest wizard in the city) or Mort or anyone else? What's Kim's connection to the dark side?

Plus, the blessed kerchiefs the Knights wrap dropped coins do in seem to be able to block the summoning. And that's just a portable field measure to secure them for transport, so it stands to reason that their coin jail monasteries have better countermeasures.  On the other hand, it's also possible they're mistaken about it being the kerchiefs (they do get a fair bit wrong about the Lash situation) and it's actually the presence of the Knights themselves, or near-saintly priests like Forthill, who are jamming the summoning like they jam Anduriel's listening.  Rotate the wrong dude out of the monastery, and the merely averagely-good personnel no longer pose a problem to Nic and Tessa rubber-banding their crews back to them?

As for the Kim theory, she doesn't necessarily have to have a particular affinity for the dark. Kumori seemed more like a deluded idealist, with a side order of healthy fear of how easily Cowl could kill her if she accepted Harry's suggestion to turn on him.  Telling her that he could reverse her necromantic resurrection - or convert her into a regular controlled zombie if she got out of line - would be a pretty effective stick alongside the carrot of learning to use dark power for her own morally good (at least, self-proclaimedly so) actions.

The main drawback I see to it is that the kind of necromantic resurrection she demonstrated with the critically injured gangster in Dead Beat seems to require the deceased to be pretty fresh. Death being a process rather than a binary, it seems like necro-healing can only catch them up to a certain level of how far gone they are.  So if Cowl had snapped her up as an apprentice acquisition of opportunity after MacFinn killed her, the window of opportunity is almost certainly before she made it to burial. And while I'm sure he could do that easily in and of itself, it would leave a missing body where the official system is expecting one to be accounted for. Given Karrin's interest in her, that seems like the sort of thing it would be a stretch for her not to notice and end up questioning Harry over.  Not impossible if he was using mind magic really widely to cover his tracks, but still a pretty big stretch.

I will give credit that most of the Kumori theories have been blind to the possibility of Cowl bringing back a dead character, though. That bears considering.

I'm pretty sure there was a WOJ that, at least, archangels aren't susceptible to Nemesis because their nature is immutable.  Maybe he wasn't speaking to the lower orders of angels on that point because he just wanted to keep readers guessing, but the omission seems striking.

On the other hand, it's not impossible that some of the Fallen - being treacherous by nature - might make a calculated decision to go over to the other side for rewards under the new Outsider order, rather than being compelled by Nemesis.  Or the infection might be of the host rather than the Fallen.

Regarding Namshiel though, I think he's the misdirect, with Tessa and/or Rosanna framing him as the Denarian turncoat.  Marcone isn't an innate talent, or at least he's a very minor one if he has any juice at all - most of what he's doing relies on Namshiel's power. All it would have taken to ensure Nemesis' success in BG would have been for Namshiel to turn off the tap at the crucial moment.  That suggest that while Namshiel is still a dick, he's acting on his own purposes rather than the Outsiders'.

As for Arctis Tor, we don't actually have Mab's reasoning for believing he was the attacker (for that matter, she didn't actively confirm Harry's guess that he was, either, she just stayed silent to it). But I don't think it would be beyond Tessa's abilities to cast a disguise that would pass for Namshiel so long as she didn't get too close to Mab.  Just choose a spiny battle form instead of her usual one - or even cast a high quality illusion of one - fry some foot soldiers from a distance, and boom, you've got a patsy set up even if the attack fails.

Besides, on all the other occasions we've seen Namshiel fight, he seems to have a preference for more esoteric forms of magic over raw fire - I suspect it's an egotistical streak.  I suppose it's possible the attacker really was Namshiel and he was just resorting to crude fire because it's a good counter to lots of Winter troops, but it seems more compelling that someone less talented was posing as Namshiel.