Okay. So, let's talk
worst case.
Before we get started on what might have happened, we need to start with why and how it happened in the first place. That dream Rathan had back in
Chapter 8 of Family Matters? Specifically this bit?
"And then there was a bit where I'd nearly got free and then there was this heat and hunger and it burned me, mama. And it was like I was fighting over something but then something else ate what I wanted before I could have it and left me alone in the dark all burned. It was scary. And mean."
That was Haneyl stealing part of Envious Heart, because she was Keris's envy and greed and made the (metaphysical) case that she had a better right to it than Rathan from a Principle viewpoint, even if he had better elemental resonance with it. As such, it got split in half - Rathan got the sapping ruinous envy that ruins and pulls down its targets to lower than him, while Haneyl got the burning self-improvement envy that builds itself up to exceed its target. What this meant was that Haneyl reacted to the mercury differently than the RAW Envious Heart mechanics, since she only had one half and her nature warped it more. Where Keris has the target-envy-outdo-regen-WP cycle, Haneyl accumulated mercury every time she saw someone better than her and subconsciously autotargeted them,
then transmuted it into fuel if she surpassed them.
This fuel was, importantly,
still mercury - just now in a metaphysically "burnable" state that contributed to her fuel gauge. This is part of why her romp through the South topped her up to
horrific levels. She had more mercury than wood in her fuel stores by the end there; that's part of what was wrong.
More importantly, when she
failed to surpass her targets, the mercury bioaccumulated in her flesh, making her more envious - and lowering the threshold at which the effect autotriggered when she saw someone with more X than her, where the constraints on "X" got broader and broader as well. At first it was just people like the Tengese Prince;
way above her in wealth and political power; things she centrally wanted as part of her core nature. By the end it was people who were only a
little better than her in unrelated or secondary things like fighting or acting cultured. Or, of course, the mere
existence of her mother as someone who's simply more powerful than her at a metaphysical level.
So. What could have happened? Well, for a start, if the situation had been left as it was with no intervention, it would have been an even toss-up as to which would have happened first: the bioaccumulation making her collapse and start exhibiting palsy symptoms or her envy triggering a burning. In practice it leads to a burning either way, the coin toss just decides how badly poisoned she is and what the end result looks like afterwards.
If she'd undergone a burning, then, several things would have happened.
Firstly,
all of the mercury in her fuel store would have gone up in one go, holy shit. In the real world, this instantly kills anyone nearby her when she goes off as she literally
detonates in a Sapphire-Sorcery-scale cataclysm that would have poisoned the area and got mercury into the groundwater and probably also the ocean around Saata, like a major industrial accident. It wouldn't have had a major effect immediately, but that's because it's not in mercury's nature to be so obvious quickly - instead, anyone eating fish from the sea or drinking water from the contaminated wells around Saata (which everyone there does, there's not enough land to avoid either) would be building up neurological poison in the months and years to follow.
That's Creation, of course.
In Krisity it would have been much, much worse.
What would have been a Sapphire-scale detonation in the real world would have been the
entire Swamp going up in flames inside Keris's soul, releasing all of that mercury-fuel as toxic vapour into the atmosphere. Spreading so much mercury through Keris's soul - which would have been blown counterclockwise around the Far Directions by the Cloud Wall - would have been very, very bad. It could easily have either poisoned - or maybe worse,
tainted - her other souls, especially Sirelmiya and Calesco who are immediately downwind of the effects and Zanara, who's upwind but right next door. Rathan would have been safest, from upwind distance and mercury tolerance - but even he would have felt the effects of so much quicksilver getting forced into the water cycle and likely become ill in some way.
What about Haneyl herself? Well, most if not all of the plant life in the Swamp would have died off, depending on how badly she was poisoned before the burning. If it had killed off all of it, the Swamp would have stopped being the Swamp entirely, and the Metagaos in Haneyl would have died; turning her into a mad spirit of demonic fire and poison ruling over a bubbling toxic wasteland lit in green and constantly shrouded by fumes. Zanara would have probably been the one who regrew Metagaos, losing their own Szoreny in the process. Keris would have been changed by the reconceptualisation of her major Principles, and probably not in a healthy way. Also, she would have been really upset by one particular aspect of Haneyl's change, even above and beyond the fact she would now be a mad toxic spirit. It would have killed all her keruby, even if they were out of the blast. Apart from maybe the fleshless flames - Saji might have come through merely "changed", rather than "unmade". But she'd have lost Rounen and Elly for sure.
If some of the Swamp flora had survived, things would have been better... but still not good. Physically speaking, the bioaccumulation in Haney's tissues would have boiled, and probably "cooked" in her flesh - in the sense of permanently altering the makeup of the ingredients, a'la "you can't get the flour and sugar back out of a cake once it's baked". In its raw liquid state, Zanara was able to extract the mercury in its entirety by keeping Haneyl simmering but not actually burning long enough to draw it out into her blood (and then ripping it out along with her heart). By contrast, "cooked-in" mercury would probably have left Haneyl with permanent symptoms of mercury poisoning that would have required lifelong medication - represented and mirrored by the regrown Swamp plants being sickly and mercury-laced. This would almost certainly have resisted Poison/Crippling treatment due to being an affliction of her essential nature rather than her literal physical body - something more of a nature to Autochthon's sickness in how she would have made it part of who she was. It might have been curable, but at the very least it would have been an order of magnitude harder than just using anti-keyword Charms. Haneyl would in effect have become an ill girl waifu like Lilunu; scarred by her refusal to let go of something that was toxic to her.
Now, don't let this convince you that Zanara was fully in the right, either. Their motives were, in a very thematic way, two-faced. On the one hand they they were sincerely terrified for their big sister and wanted to help her by any means necessary. But on the other hand they wanted to steal Envious Heart and the Szoreny mind tree for themselves, and not lose it in favour of Metagaos. Both were true. Two reasons for the same action. Also, ironically, Zana is the closer one to Haneyl - which implies the "scared for big sis and wanting to help her" motivation was the
Zana part of their personality, despite her usually being the bitchier of the Zana-Nara pair. Meanwhile Nara was the one who was, in a metaphysical sense, quietly stealing Rathan's rarely-worn clothes out of his wardrobe every time he went over without a hint of shame until he'd emptied the entire thing of Rathan's brief punk-rocker phase outfits.
Could Zanara have handled this better? Hard to say. Could they have handled it
differently? Without a doubt. There were certainly other ways they could have done it. They didn't have to do what they did. But they didn't feel they could tell Keris and get her help with it because they know that the souls reflect Keris's feelings - and whatever else they might have lied about; they were damn right that Haneyl would never have given anything up willingly, even if told how it was harming her. With Keris out of the picture in case it tips off Haneyl, Vali and Calesco are immediately out for the same reason. They don't trust Dulmea enough, and they'd been stealing from Rathan too - he didn't seem to mind, but his Payback nature might have had him oppose their plan anyway, to say nothing of how he wouldn't really have been
useful and if he wasn't needed they saw no point in risking a leak by telling him. And while they might very seriously have considered telling Lilunu, they didn't get to go back to Hell last Calibration, so there was no opportunity.
They
did tell Eko; their opposite number and the other soul who's pulled off a complex soul-modification scheme. But even then, they only told her because they knew she'd help with the problem-solving bits out of concern for Haneyl, and then forget because she wouldn't want to think about doing mean things for her little sister even if they were necessary. That wasn't trust - they
knew how to phrase it to get her to accept the need for action, agree to go along with their solution rather than spend more time on a hard and painful topic than absolutely necessary, and then not want to think about it any more.
And by Zanara's inherent nature, their solution was going to be big, showy, and melodramatic.
Thus you have it.
