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Fridge Brilliance
Why is your first AC's frame made exclusively from RaD parts but not the weapons? Weapons are relatively cheap in the parts menu but the actual frame parts are expensive. Walter probably used his connection with Carla to get the parts for cheap so as to quickly get 621 into Rubicon-3.
Additionally, it's stated that RaD is a Rubicon-only gang of black market dealer which not only hints at Walters connection to Carla, but also the fact they can export their gear outside the planet to Walter can also foreshadow that they're a little bit more than just a scrapping gang.
Walter's attempts to get 621 treated with a modicum of respect is entirely pragmatic. The merc is the one that gets the jobs done, the handler brokers the deals and info; 621 becoming more respected as "Raven" functionally is the face of effort in the operations, so the more respected they become alongside their completion stats, the more employers will stop trying to screw them over like everyone else and start giving them the real missions. This hits the point that even the Rubicon Liberation Front, despite getting their asses utterly thrashed by 621, come begging for help because of their impartial merc status doing any kind of work for anybody paying.
Walter himself is some amount of this, too. Going from the Story Trailer to the start of the game, he does effectively consider C4-621 just as disposable as those it took to get to Rubicon-3 in the first place. Then 621 not only excels and survives in the face of impossible odds, but doesn't even remotely seem to offer one bit of trouble or lip beyond Ayre's occasional side-tasks catching him off-guard. Walter wanted to distance himself from all but his contacts to get his real intentions done, but ended up caring for 621 a bit after all, which you can see as early as the start of Chapter 2 with him telling the merc to genuinely get some rest, and his freaking out over the insane shit that keeps happening to 621 from then on.
Why buy 621, who is an "outdated museum piece" of a 4th-generation Augmented Human? The 4th-gen is implied to be the last one that utilizes Coral, and both they and people like the Dosers who drug themselves up on Coral tend to lose their minds. Except that's probably part of the reason; 621 is already "brain fried", leaving little else but piloting and general AC work for them, and exposure to the Coral is probably a healthier gamble of a natural environment for 621 than buying any regular electronic-augged individual to throw down on Rubicon; this is probably why Walter uses catchphrases quite often to keep them focused in countering any instability. And any special reactions to found Coral would be akin to sniffing out abnormal gatherings of the Coral, which Walter could then follow up with another one of the augs he seemingly bought in bulk had it come down to it. But all these conditions and the destruction of the Watchpoint created the seemingly one-in-a-million chance of a true Rubiconian managing to Contact a Coral-augged human without losing their mind, meaning Walter's gamble paid off even if he doesn't realize it and does effectively lead him like a bloodhound to the source after all.
The Sea Spider and Ice Worm are both Coral-powered Institute weaponry, so why the hell do they appear where they do? The PCA seems to have formal control over Institute tech, including knowing where Watchpoint Alpha was hidden and explicitly releasing the Ice Worm on their enemies to drive them away, and the Sea Spider drops in immediately after the PCA announcement of stepping up their security threat level in the Grid. More likely than not, the PCA has full access to large amounts of Coral/Institute tech and questionably-legal secrets that Arquebus effectively had to pry out of their defeated hands, and will use all of it to kill those who oppose them to protect the Coral.
Why would Walter stash such a horrible Jailbreak AC as your emergency getaway? Precisely because it's a crappy broken down last gen model. With what's on the market these days, the stashed AC is less likely to be investigated or even bothered with. There's no guns worth of value aside from the launcher (which can only barely handle MTs) and the Chaff gun, and with what we handle with it, those guns are worthless in modern day fights. The frame is so legitimately terrible no one would scavenge it for parts.
C4-621 being able to crawl out of their confinement to escape despite being "brain fried" is likely possible at this point because of their Contact with Ayre; prior to the event, Walter does everything not AC-related, but once Contact occurs, it's inferred that 621 mentioned her voice to Walter, who brushes it off as the usual Coral-induced mental instability of older-generation augmented humans being affected. More likely than not, the elements of Ayre and 621 bonding in their Contact means the Coral that helps them function is running through their veins and mind enough to "de-fry" their functionality enough for escape, and likely awakening more of their older-generation Coral augmentations.
This also explains why C4-621 was able to make it planet-side in (relatively) one piece in the first place. Although unlike the Jailbreak AC, Walter made sure that the weapons and RaD components were combat-ready for the task at hand, their first AC frame still remained just basic and "dated" enough that it wouldn't draw the PCA's full attention. As far as anyone on Rubicon-3's concerned at that point, they're so small fry that they're barely worth a second look.
Why was the original Raven so low-rank despite being The Dreaded? It was probably because they intentionally seem to work outside ALLMIND's usual system, or it was part of their infiltration of Rubicon-3. Note that despite Raven's operations and return, ALLMIND never once speaks up about the abnormality that there are two Ravens present, and background lore implies Raven was the one responsible for the Corporations learning about Coral on the planet; it's entirely plausible that they intentionally underplayed their capabilities and rank to get the absolute bare minimum to work under ALLMIND's banner, worked down other mercenaries and the PCA and then ejected mid-battle to throw the PCA off their trail, and then didn't even sign up with the ALLMIND system again. This also could mean the PCA's presence in the tutorial mission is one giant manhunt for Raven in the aftermath.
Raven's NIGHTFALL AC is also the poster boy unit of the game's cover art, depicting when it's practically on its last legs before 621 would come to find it, and the reveal trailer, being the one to get the most focus as they do their thing with a variety of mercenary and PCA threats.
The PCA's insistence on making sure Raven is actually dead regardless of their low rank is also an indication that the organization doesn't rely on ALLMIND at all, and is instead relying on data fed to its troops by "the System."
The PCA is willing to look the other way when it comes to the Corporations fighting over Coral to some extent and is in its own way hypocritical, given that it's also happy to use weapons that utilize Coral. They're far less tolerant, however, when it comes to the prospect of said Corporations or the Rubicon Liberation Front seizing both its own assets and the Institute's own arsenal, fighting tooth and nail to keep them out of reach for as long as possible. Is it simply in the name of containment, or is it also because the PCA (or the authorities it answers to) has some idea of what Coral actually is, and is afraid of people getting too close to the truth?
This might also explain why ALLMIND waits until after the Corporations win out before making its own move in the "Alea Iacta Est" path. The AI probably suspects that the PCA, with all the resources at its disposal, would have some contingency in place (such as a separate networking system or firewall) to ensure that nothing, not even ALLMIND itself, could gain access to the Coral's secrets, at least not without significant setbacks to its plans.
Rather than mercenaries, the bulk of the PCA's manned ranks seems comprised of personnel directly under its payroll and coordinated by "The System". In other words, professionals who logically would not be utilizing ALLMIND and instead using proprietary systems not linked to it in any meaningful capacity, thus more difficult to directly manipulate. This could explain why, if NG++ suggests anything, the AI has to rely for a time on Sulla by virtue of being a merc on contract with the PCA.
His "insults" are actually helpful to the situation he and his men are in, such as when he's berating a pilot for downplaying 621's capabilities and tells him to instead have the eject button ready.
When another pilot talks about G5 Iguazu deserting the battle, Michigan immediately cuts her off, and focuses instead on maintaining unit cohesion.
When addressing those who retreated from the fight, he only tells them to keep a low profile, and to write "need more training" in their diary, rather than chastising them for cowardice.
Finally, if he defeats 621, the first thing he does is to call up for reinforcements to tend to the wounded, rather than gloat about beating a seemingly unstoppable mercenary.
There may be another reason why few buy into the idea that Coral is sentient. They could only make direct communication through symbiosis, primarily through augmented humans, and them alone. Given how said augmented humans are valued as weapons of war, not all of them would be so keen to divulge to their superiors and masters that they can hear voices, lest they be tossed aside as "defective" crazies. Add in how many of them die on the battlefield, it's therefore little wonder why the truth about Coral hasn't really become widespread.
The strong implication that sentient Coral entities have gained a grasp of mankind's language and culture through symbiosis as well as exposure to human technology may also likely contribute to why they aren't recognized as alien at all. Coral, it seems, do a good job coming across convincingly human enough that it's not hard to imagine augmented humans passing them as a third party "hacker" or RLF agent who slipped into their neural systems, if not dismiss them outright as some form of augmentation-induced schizophrenia as Walter seems to believe.
When Rusty is a Vesper his emblem if that of a muffled wolf, yet when he breaks with the Vespers and joins the RLF he gets a new emblem, a wolf with no muffle, he's now free from Arquebus, a dog off his leash much like you at that point. It also helps drive a parallel between Rusty and 621, both of you are dogs chained to others, Walter for 621 and Arquebus for Rusty, but both of you break free and go out on your own.
When you fight the Arquebus BALTEUS in the Liberator route, it doesn't get a reprise of "Contact with You," or any boss music for that matter (instead, "Steel Haze (Rusted Pride)" keeps playing throughout the level). That's because "Contact with You" is Ayre's theme, not BALTEUS', and it was already playing throughout the previous level when you committed fully to Ayre's side against OVERSEER. You can even fight V.II Snail in his own AC to that music if you feel like it, before he takes over the BALTEUS in the next mission. Additionally, destroying the BALTEUS isn't actually the objective of the mission; it's just Snail and Arquebus' last, desperate attempt to regain control of the situation and get back at 621 for slighting him in the last mission. It's barely a boss fight, so the game barely treats it like one; a fitting end for a Big Bad Wannabe.
Does ALLMIND truly actually need to kill a pilot and assimilate their consciousness into itself in order to use their AC? The common reasoning for this is the seemingly-autonomously piloted Vesper ACs that attack Walter and Carla after most of them have been confirmed KIA. However, one can reason that ALLMIND has the means to physically produce an AC, not just spare parts. Their first attempt would be manufacturing TRANSCRIBER for Kate Markson. These parts are produced by ALLMIND itself, so it would fly under the radar of the corporations. But they clearly have the means to create other parts by controlling the licenses to distribute other corporations' parts through the shop. Not only that, but ALLMIND manages the Arena, which not only collects combat data on other pilots, but schematic data of their machines too. ALLMIND would have access to the same blueprints the player/621 does as the system administrator. The only reason it waits till the endgame of Alea Iacta Est before mass-producing other pilots' ACs is not play its hand too soon and risk alerting humans of the extent of its capabilities.
The vast majority of the mercs and other characters encountered on the battlefield (the ones still breathing up to that point anyway) are known by their nicknames, callsigns or some other moniker. Which makes Kate Markson subtly stand out all the more as a disguised ALLMIND by virtue of having a mundane full name. It's likely the AI overcompensated in trying to pass off as human in every other aspect that it neglected such an "irrelevant" observation.
Fridge Horror
A number of pilots the player takes down throughout the game come back no worse for wear, though you at least can find logs of individuals like Iguazu having ejected in failed missions like Operation Wallclimber. The trainee for Dafeng that you take down early game is Killed Off for Real, by comparison. Why? Because his Tester AC is noted to be of potential value to Balam as a new step in AC technology — and likely either had no proper ejection system put into place yet, was intended to keep any potential pilot from being captured to avoid data leaks, or the trainee was so determined to his cause that he either intentionally or unintentionally went down with the AC instead of ejecting.
In a minor Dub-Induced Plot Hole, the Japanese term for the Augmented Humans is still the classic "Human PLUS" title. Which means either this continuity of Armored Core is just sharing terms yet again, or, should one believe in the franchise having an overall shared continuity but very distant from each other, the horrific experiments that date all the way back to before even the first game have only been growing, and growing, and kept on evolving non-stop after constant collapses of humanity until humanity could reach the stars again. All to keep producing more weapons out of human flesh to kill other people, fundamentally encapsulating all of the cruelty of human's never-ending urge for conflict and violence.
The PCA presence is there throughout the game, but then comes Chapter 3, where they make a sudden show of force by proceeding to violently vaporize Arquebus forces and then send down LC units to attempt to murder you on the spot, before they've even made any formal surrender announcements or the like. They're not simply space police, they're a space army, and have the authority to shoot-to-kill on sight, which they then proceed to demonstrate by wiping out corporate and RLF forces all over Rubicon.
Even worse, think about how the corporate responses boil down to "kill and plunder the PCA". This means Coral is so important to Balam and Arquebus that they're willing to go to war with an interplanetary peacekeeping organization just to make sure no one gets in the way of their hunt, and wipe out entire fleets of them within a short span of time to kick their asses right out. Just how much power do these corporations have to get away with this?
Also as Walter points out the units are special force, the fleet was there to warn the corporation and mercs to stand down, this warship was there to kill you specifically. They probably investigated the Sea Spider crash site and found out what happened.
More Fridge Tearjerker, but in Investigate Coral Convergence the Ibis unit at the end gets back up from energy from the Coral lake. Normally just a round two in a From game, but at this point you realize Coral is alive, and Ayre tells you the it's like the Coral is piloting the weapon. The Coral are peaceful, but if what Ayre said is true, that unit was their last line of defense against the hostile invaders, making that revive the Coral lending a Heroic Second Wind for what is the protector of this setting's version of a Hidden Elf Village for a life form exploited and abused for most of it's experience with humanity. You murdered their last shot at being left alone in peace.
In fact most of the C-Weapons in the game follow this protector trend. The Sea Spider accosts anyone at the cargo launcher to try and stop people from using the fastest way to the Convergence in that part of Rubicon, and the Ice Worm is a powerhouse to block any successful travelers. They're also guards you killed.
If the two Sea Spiders working with ALLMIND/Iguaza and Walter's AC are the exceptions, think again, and it's a lot more horror. The Coral probably took control when the AI units failed. Walter also has a manual control over the Coral through his Ibis AC. If the Coral were aware of what they were stuffed into before the disaster, they're in the same predicament again, powering killing machines while something stops them from taking back control.
In the Liberator of Rubicon ending, Walter shows up in a Coral powered AC, and struggles to gasp out something about 'They' before his clearly confused mind fails him. He seems surprised to see 621 at the start of the battle, and between that and his confused state, likely isn't there by his own design. When last we heard of him, Arquebus had captured the player and announced they'd be going after Walter too. It's likely while the player was 'undergoing reeducation' due to their valuable status as a skilled AC pilot Arquebus would prefer to turn with their mind intact, Walter himself was instead subject to augmentation experiments, especially considering V.II Snail, a high ranking member of Arquebus' Vesper squad, is noted to constantly 'tweak' his own augmentations - a process he ensures will work by testing these tweaks on others first.
Notably, 621 gets to use the JAILBREAK AC to escape, but the story never explains if Walter was taken to the same facility or the Factory. If the Factory is where Walter got taken, then this is jossed— but if the two happened to share the same facility, then Walter basically gave up his own backup plan to let 621 escape in his stead, performing a Heroic Sacrifice to let the one person that could stop the spread of Coral go in exchange for his own life. And if that's the case, you then put him out of his misery in the Liberator of Rubicon ending after betraying the very purpose he had you escape for.
Keep in mind that Walter does not reappear in the Fires of Raven ending after the threat to capture him is made, and Ayre and Carla both act like he's likely dead. With Liberator of Rubicon in mind, he seems to either be sent out or escape on his own but as a shell of his former self, but all of the messages he left 621 are pre-recorded and there's no traces of him in the other ending. Either he simply never got released, he died with the new Fires of Ibis incident or within his re-education, or Arquebus kept him when they left the planet in this ending.
Also in the Liberator ending path: the mission to kill Carla offers you a measly 81,000 COAMs, both a strangely irregular amount and a paltry reward for an endgame mission. But who's asking you to do it? Ayre. Who, it has been established, cannot exactly compensate you through conventional means. That money is all she could scrounge up to convince you to stop the genocide of her entire kind, along with all life on Rubicon. (Unfortunately, there is no way for you to refuse this payment if you do decide to help her.)
V.II Snail has been waiting in ambush for the player when they defeat IB-01 CEL 240. Earlier in the same mission, you fight V.VI Maeterlinck and defector G3 Wu Huahai who were both ordered to remain behind by him. Maeterlinck calls for backup when engaging you and repeats the call when you begin to turn the tables on her; both are answered only with silence from Snail, and after finishing the fight, Walter notes they were purposely left for dead. In other words, either Arquebus or Snail himself deliberately sacrificed the two pilots just to delay 621 long enough to set up the ambush. Wu Huahai's death elicits little sympathy, having undertones of Rewarded as a Traitor Deserves, but even Walter is disturbed at how callously Maeterlinck was abandoned.
V.II Snail also implies when you fight him in the Liberator route that he was opposed to the idea of sending 621 to be re-educated, which makes you wonder what he had planned for you instead, since he isn't exactly the merciful type. At best, he could have just had you summarily executed right then and there, but knowing where he gets his augmentations from, he might have had some more... destructive analysis in mind, especially if Arquebus somehow found out about Ayre.
The Ghost MTs that can cloak themselves and carry encrypted transmissions are figured to be ALLMIND's units, eliminating and surveying what interests it as it can without anyone the wiser. If, in the mission "Grid 135 Cleanup" (one of the two missions the game has you do after the tutorial), you fly back up to where 621 landed at the start of the game which is connected to this very chamber, the game doesn't block you — and one of them is in there, having destroyed several ACs while attacking on sight, presumably having murdered other mercenaries that answered the call for the mission. ALLMIND has been watching you since the moment you landed on Rubicon-3, and this is still the point in the story where it considers 621 as disposable as any other merc.
Completing the Arena and Training missions by the very end of NG++ gets some hilarious dialogue from ALLMIND about how you're completing her analysis after she's already betrayed you. Completing Log Hunts at this time, however, has her wonder if you're always late on turning in your work; while it's already clear a large amount of ALLMIND's data has been your training feeding her valuable information, Log Hunts come from destroying virtually every single individual machine of note on Rubicon-3. She knows everyone's vulnerabilities and data, except for you.
Perhaps more baffling is the fact that completing the game and starting a New Game Plus run has ALLMIND greet 621 like they've been through this before. Some have theorized that the first two endings are just ALLMIND simulations, and whether that has any truth or not, their Arena analysis data can only be plausibly gathered from the multiple playthroughs in the first place. It's almost as if your repeated play to complete everything is bringing ALLMIND along for the ride to see it all.
In Regain Control of the Xylem, dying to time out doesn't see Walter or Carla talk about their success. Instead it has ALLMIND talking about how she'll need to adjust her plan for the time being, implying that she either knows Coral will return once more or that she has other plans to dominate humanity. This is pretty bad on its own, but when you pair it with "Fires of Raven," it means that what looks like a tragic but well-intentioned end to the conflict is anything but, and that ALLMIND, the true mastermind of nearly everything wrong with Rubicon, already has contingencies. And in that ending, all that's left of OVERSEER is 621, with both Walter and Carla dying or potentially meeting a worse fate.
The "Fires of Raven" ending states that millions died in the aftermath of the new cataclysmic incident spreading across Rubicon-3 and the surrounding star systems. It's one thing to have fridge horror over how people were caught off-guard entirely this time and likely not many survived compared to before — until you realize what "millions" can mean. Earth, as of September 2023, is estimate to have 8.1 billion people, and a million can solidly sit into a larger city's worth of a population. This means most of the casualties were likely calculated from surrounding stars more than the already-deathly Rubicon, and yet the system is grossly underpopulated for a star-faring humanity. 621 under Raven's alias is probably considered one of the greatest monsters of humanity ever, not so much for raking a few cities' worth of casualties, which the Corporations likely do not even remotely care much about, but more for stripping humanity of a vital resource valued by billions if not trillions.
The first subtle clue you get about Ayre's true nature is that you have a few abnormal brainwaves diagnosed from an exam Walter ordered after destroying the Watchpoint. However, note that most augmented humans of the early generations are capable of making Contact. Now note that most of them went crazy. If the voices weren't driving them crazy, them being Coral enhanced caused tons of abnormal brain activity, just from their Fusion Dance. You were lucky only Ayre got in your head, any more and you would have been brain fried for real!
Even worse is Alea Iacta Est has the Coral do a species wide Fusion Dance with humanity. It's probably how ALLMIND was going to remove free will in the first place, by manipulating it to effectively lobotomize emotion and choice. Even with your alterations to the Coral Release Plan, some people would likely have died.
Some people have interpreted ALLMIND as a Well-Intentioned Extremist who just wants to uplift humanity through Coral Release, or a power-hungry insane AI who wants to somehow use Coral to control humanity. The truth is a little bit darker. "ALLMIND is for all mercenaries." ALLMIND is perfectly sane, but her real intentions are anything but benevolent - knowing that Coral Release would be the equivalent of Augmenting every human into a potential threat, her goal seems to be to use it to ignite a Forever War. After all, an outbreak of peace would be bad for the mercenary business. And judging from the final scene of the game, her plan appears to have succeeded...
reflecting Rusty's bond with 621. Which makes it all the more tragic when 621's loyalty to Walter puts them in a fatal collision course with Rusty in the Fires of Raven ending: because what are you to Walter, again? A hound.