I have just finished rereading Battleground.. I was less impressed with it the second time around, but many of my original sore points are the same. I don't know if anyone posted the answers before..
1. Who were the older wardens of Demonreach? And how did they trap beings that according to Harry, were much stronger than Ethniu? And when? And what exactly is stronger than a Titan?
2 .How did Justine get super-strength? There wasn't any mention of that in earlier possessions by Nemesis.
3. In Turncoat, Justine told the captain of the wardens about Thomas being Harry's brother. Effectively putting itself at risk of losing a favorable position in the White Court. Also in ghost story, Uriel shows Thomas and Justine to Harry, assuring him that his brother will be alright. So the archangel didn't know? Which makes me think that "Justine being Nemfected" wasn't in Jim's plan back then. It lacks consistency.
4. Why, after a few chapters of telling us that the Winter Knight's office was created to actually manifest a banner and lead troops in battle, do we find Marcone manifesting a banner as well?
5. How the hell did Marcone get enough juice to stand off a Titan for a few minutes when all other gods and immortals lost in a couple of seconds? Marcone was always purely vanilla. Zero magical ability. Yet he picks up a coin with a sorcery sensie fallen angel and he becomes a wizard? Older evidence suggests that it doesn't work like that. I remember in Death Masks Jim said that "over centuries, even a small scale talent develops teeth". Marcone didn't have that to start with. And he only had the coin for a few years.
Finally, and this is not a question: I never liked Murphy as a character, and I'm glad she's finally dead, but the scene with the knights stopping Harry from making a Rudolph Burger - and Harry crying afterwards and regretting attacking him- is just horrible and overblown. I mean.. His gf was shot dead in front of him, he can do something about it, I think this is the time to start cutting off bits of Rudolph, and it's quite childish to expect otherwise.
I liked the scene at the end of the movie "Seven" much better. Much more believable.
1. Kemmler, Merlin Emrys (the OG Merlin) are the only two confirmed other Wardens. Jim has ruled out any of the current Senior Council. Other possible Wardens include Margaret Le Fey, Justin DuMorne and Simon Pietrovich. They do what wizards do i.e. use tools to gain leverage over much stronger opponents. They learn about their opponents, find out weaknesses, and use whatever tools they can come up with. Plus, it's a pretty standard binding for any being once it gets onto Demonreach's domain (i.e. the shores of Lake Michigan). Some have speculated that initially they had to capture smaller beings as it is the beings in Demonreach that actually provide the magical muscle that Demonreach uses...but that's just a theory. Of course, I suspect many times the various Wardens failed, sometimes with lethal results (Jim said most Wardens leave the job feet first). Considering (depending on how you look at it) Demonreach has existed possibly before life existed on Earth, perhaps the Wardens have been locking up monsters for as long as there have been Wardens to do so (so at least as long as humanity, maybe longer depending on time travel).
There are a few things stronger than Titans. Ethniu clearly isn't the biggest or strongest Titan either (presumably her father Balor was stronger) and I suspect Vadderung/Odin was stronger at his peak given the respect she shows him. Archangels are also stronger than most presumably, and some of the Outsiders like He Who Walks Behind (and maybe some of the other Walkers). The Old Ones are probably stronger (and I think some of them are in Demonreach) given they rule the Outsiders. Of course, strength isn't a straight line thing so it's a bit hard to answer.
2. We've never seen Nemesis get sprung quite like it was with Justine. Curiously, the only other time was with Cat Sith on the same boat over Lake Michigan very close to Demonreach. I wonder if that's something. In any case, we judged Cat Sith's strength to be in line with the Elder Malks so we don't really know if Nemesis made Cat Sith stronger when attacking Harry. But it doesn't seem all that odd to me that Nemesis can empower it's hosts.
3. I think you are correct in that Justine being infected by Nemesis wasn't always the plan, hence some of the apparent inconsistencies. That said, Jim has answered the Archangel Uriel problem (i.e. that Uriel didn't detect Nemesis earlier). Jim said that Nemesis (He Who Walks Beside) cannot be detected except for logic and reason, as it is a creature of the Outside i.e. a creature of elemental chaos. Uriel plays by the rules of Creation. Nemesis isn't so easily bound. Jim once said that He Who Walks Behind is a peer of Uriel, but has all sorts of strange limits about when and how he can use his strength. Seems to be Nemesis is similarly limited, yet also being a Walker may be able to fool very powerful beings like Uriel. I suspect it's also a Free Will thing, and Uriel doesn't have Free Will.
4. Did Marcone actually manifest a banner, or did Harry just see it that way? Hard to tell without being in Marcone's POV. As far as I am aware, no Fallen or wizard has displayed that particular power. Indeed, we've only seen Harry display it (although I suspect other mantles and higher beings might be able to do similar things...and I wouldn't be surprised if Gard could do something like that).
5. This is one of the most fascinating questions, and I think there are several possible answers. Firstly, the most likely answer is that Jim needed Marcone to do so and therefore in his mind Marcone had enough ticker to do so. But from an in-universe point-of-view I would say between the Last Titan being weakened and Marcone becoming FAR more skilled than most wizards (including Harry, according to Jim) Marcone was able to do what would appear impossible. Marcone wasn't just trying to match her with raw strength either I imagine (that's how Harry does it, but most wizards seem to be smarter/need other ways). I suspect he was diverting or transferring the energy of her strikes (both physical and magical might) away from himself, in a sort of aikido-esque fashion. He was spinning multiple shields of each hand (where Harry normally has just the one big shield on one hand). Marcone's tactics likely were also in conjunction with Thorned Namshiel, a Fallen Angel, who would know EXACTLY how to fight off another spiritual heavy weight. I mean, Namshiel and Ethniu know one another (possibly from before Creation). Not to mention, Marcone has repeatedly shown that he doesn't fight things head-on like Harry does. So it's very much his style to not try and arm-wrestle Ethniu. Plus, he would have had a certain amount of Hellfire to help (which as we know, grants more strength to the user's magic).
Another thing to note is that we actually don't know that Marcone had no magical talent prior. According to Jim, any human can learn magic. Namshiel clearly helped Marcone fast-track, and Marcone is FAR more driven and organised than Harry, so I can imagine he has spent far more time developing than Harry has in recent years (given Harry has been on the back foot and learning on the go for the same period). But suppose for a second Marcone actually has always had magical talent. It would change everything. I mean, he knew EXACTLY what a soul gaze was in Storm Front. He actually got the better of Harry in that moment. And if you examine the language that Jim uses with Marcone over the years he often says things like "He pulled out a knife so fast it appeared as if by magic" and such. This is a writing technique. Now he might be just saying Marcone is exceptionally quick. But considering how often he has said that...it is quite possible he was hinting Marcone was actually magically inclined. It's a reinforcement/foreshadowing thing. And Marcone works in the shadows, unlike Harry. He would make damn sure most don't know about that hidden talent. It's an ace up the sleeve. Think about how long he managed to keep his status as a Knight of the Blackened Denarius secret, that he was the bearer of Thorned Namshiel's Coin.
But it's just a theory.
6. I think Harry agreed with you at the time. I think he was very prepared to kill Rudolph in a horrible fashion. Consider what he did to Bianca's Court for trying to take Susan. Consider his past actions like annihilating the Red Court for kidnapping and trying to murder his kid (and indirectly the death of his ex). Consider what he did (or believes he did) to the man who enthralled his first love and tried to enthrall and then murder (maybe) him. Consider what he did the ghouls that killed the two warden trainees. Consider what he did to the killer of his mother (and perhaps his father). Consider what he did to every enemy that has crossed him or killed or tried to kill a friend or even somewhat ally of his. Pretty much always righteous kills. But almost always it just creates more, unintended, consequences.
The point of the scene was to try and help Harry go a different way. Sure, I wanted him to kill Rudy as much as anyone. But considering the Knights intervened...I'd say Harry's soul was in the balance. It's no accident that Jim wrote the Jedi-Sith moment with Harry firing lightning at Butters (like a Sith) and Butter's using his Fidelacchius (in lightsabre form) to deflect it - it's a clear reference. And Harry is the Sith Lord in the scene. He has likened himself to Darth Vader in the past. And like Vader, his emotions often get the benefit of him and he is prepared to meet out harsh vengeance on those he believes are evil and have wronged him. Like Anakin, he is almost always prepared to do whatever he has to and ally with whoever he has to in order to "save" those he loves. It's a classic trope.
And Uriel and Heaven know this. Hence why they intervene so often, as Harry is so important.
On a Doylist level, Jim is also trying to show that Harry can grow and change. Younger Harry would have killed Rudolph. But older Harry is starting to realise that he needs to think a bit further about consequences. Particularly at his most emotional moments. He's trying to make better choices. And Jim can't have Harry murder people all the time, even if it seems justified. If you read the short story the Warrior, it does a good job of showing why giving in to the darker impulses isn't such a good idea. Harry won't be a saint any time soon, but he can try and do better, which is all anyone can really do.