Magdha Sprenger should have died when she was blasted off of the Tor of Dominance by Mellis Screamtaker.
She did not, because she Burned A Fate Point, which she was in possession of by virtue of being the most blessed and chosen of Manann's holy priests sent forth by Manann to take stock of His Cult and reform it a bit while cutting out the failures and corruption. She is also blessed with natural waterbreathing capabilities due to being one of the minor but especially faithful sects of Manann's worshippers, the ones who live out at sea and never step foot on land, yet who are always seemingly able to maintain and repair the ships that are their homes. So she hit the water, died didn't die, and was half-dead while being dragged filtered down through the systems of the Ark to be deposited like refuse out into the open water. Instead of floating away entirely, she latched on like a barnacle to the underside of the Ark, and blearily and angrily focused on maintaining a thin line of mind and sanity. Unlike Isha, Manann is very rarely a perfectly kind and loving God, so Maghda is not in picture perfect condition, half of her body was practically burned away, and has now been 'fixed' with, well, the sea. She's been marinating in the energies of the Dhar Anchorstones that is extremely diffused as not to, you know, poison the entire ocean outright before it could be cleansed/washed away/etc. by magical currents, aetheric pulls towards the Vortex, etc, but it is a sort of power regardless given how close she's clung to it. Every single turn, she's been rolling successively to slowly build up enough power and connection to the ocean, her God, and the Anchorstone, and other beasts, while clinging to life, eating what small ocean life that can be coaxed into her mouth. Normally, this sort of thing would have gone noticed, but due to the decimation of the Coven during their small civil conflict, Alyssa focusing on other things like her Auction, and Magdha successfully sublimating her works into the general magical frenzy just beneath all Arks which helps keep them afloat, it was not. Not until she finally reached out and struck, with Divine power, to fracture one of the Dhar Anchorstones complexes from the bottom where it touches the water directly, which caused it to essentially, and literally, explode like a reactor going up. This destroyed an entire Anchorstone nexus, and in turn, killed around a thousand or so Druchii working it over as slaves and adjutants performing minute adjustments from day to day, doing more menial tasks, and guarding it. Guarding Anchorstones is very important, so some of the more elite troops on the Ark were present as well as guards, and they died as well. Other Druchii died as Dhar fallout started to spread around the immediate area despite the best efforts of the three sorceresses sent to try and contain and investigate the situation. The Cult of Mathlann was focused very much on the docks, and had some of their people at the Anchorstones as well, so they've been damaged by this as well, losing a few priests who were starting to feel that something was off. There are other sea beasts beneath the Ark as well, yes, and Maghda had also been spending time making them not attack her, and also drawing others to her side as well.
She caused significant, major damage, as doing so has actively stripped the Ark's magical capabilities and capacity by a significant amount. It is slower turning, in movement, and is lessened in defenses. To whit, it was going to come up in the update itself from Natasha's perspective, but there is literally less of a 'cloying' feeling over the Ark restricting magic from being cast, from coming from, and going to, the Ark. By doing so, she has in fact made the Ark easier to 'sense' and 'see' for lack of a better term, by others, while also allowing herself, Maghda, to not have to work as hard as she is. She is clinging to life and the Ark as a literal holy barnacle, who is absolutely unfathomably furious at the Druchii for what they've done. She's not quite who she used to be, and is unlikely to be able to serve as the High Matriarch given what Manann had to do to 'save' this favored priest of his, but she still is potent and angry, even if she's not really quite in her right mind anymore, or ever will be again. But she does have a cause and a purpose that she's sticking to, again, like the aforementioned barnacle. She is also doing this because Manann himself is angry at his temple-ships being destroyed, and also because Frederick von Hohenzollern made the effort and sacrifice of going keelhauling on the hardest option, and got a favorable response, which means that the mercurial and powerful Manann is throwing that much more support behind Maghda, and, though Frederick wouldn't recognize it, himself as well by virtue of pumping a bit more Magdha's way. Frederick showed himself remorseful, respectful, sacrificial, and made friends with Magdha, and that gets you points in the favor of Manann, and though he can't do anything for Frederick, he has been for Magdha, who is laterally doing the same for Frederick. So, in a way, player choice in unleashing the Witch Hunters, followed but going down to Marienburg, to doing the keelhauling the way they did, to making friends with Magdha, to speaking with her afterwards and forging a stronger bond, has led to this result which in turn killed many Druchii, damaged the Ark more than any of the bombs that Hultressa set, and cracked Alyssa's mind that much more, damaging her decision making and control and status significantly.
Hammer Pope and Wolf Pope back during the Vampire War, unfortunately, used up their Fate Points in the GWAC, so didn't have any when Zacharias came through on them. It was a careful decision made, and perhaps a bit unfair on the side of 'good', but I still don't really plan on giving evil characters Fate Points, because, well, I'm already playing them against the players. So unlikely to see, say, a powerful Chaos Lord have a Fate Point, but Magdha? She's specifically noted to be potent, and well favored, and summoned by Manann himself for the Cult of the Old World to listen to.
As for Hultressa, Gwendolyn, Alyssa, and Eldyra.
Gwendolyn managed to escape, because Eldyra went full 'Heroic Squire' on the Druchii that broke in Hultressa's quarters, and performed a maneuver commonly termed 'I'll Hold Them Off, Get Out Of Here'. The former did so, and the latter was fully planning on dying, but Alyssa doesn't want to let her have that satisfaction. Gwendolyn headed one direction, and got picked up by her mother, who has exhausted a lot of her resources, but also, activated a lot of traps going on inside of her own quarters, meaning that the Tor of Dominance actually had to reckon with a few released experiments, daemons, and otherwise, which is why Alyssa is partially crippled in one leg, missing an eye, beat to shit, angrier and crazier than ever, and also, you aren't seeing any other sorceresses around, because one of them died trying to capture Eldyra, and she killed them. She went and did this, Alyssa, because Johanna managed to break out a few more of her Jet anti-magic items, break some spells, and started throwing up some Ulgu spells she knows thanks to her tutoring in Nippon to help get them away, while some of the Asur actually sacrificed themselves so that the majority could escape. Currently, Johanna, Sadrina, Kerillian, Natasha, a host of inspired Asur slaves, Roland, a host of inspired Bretonnian slaves, are in the warded collapsed tower that was set up by Hultressa beforehand, who has not yet been seen since she went and got her daughter. They are currently planning on descending into the slave tunnels, the places of the Ark that are traditionally filled by only the most broken slaves that the Druchii literally do not even normally patrol down there ever because of how broken the slaves usually are. The explosions at the pyramid farm also killed a number of Druchii, some Druchii nobility, and have ruined significant food production from that location. This, mixed with the fact that other farms have been damaged, and the general chaos of the Ark, means that several Druchii notables have looked towards securing the other remaining food storage and production centers as a matter of logistical and strategic course, as in times of uncertainty, not having food is bad. This has caused them to come into conflict with one another, especially as the daemons and Alyssan loyalists are doing the same, and in some cases, the rival Alyssan Cultists are actually fighting each other to be the one to 'win' a prize here or there to present to their Cult Leader. This has caused further anarchy and damage, one of the other Pyramid Farms had fires set inside of it during said infighting, while another Aquafarm has become tainted and mostly destroyed and abandoned due to the aftershocks of the Anchorstone detonation caused by Magdha who, again, is only here because of prior choices made to ally and allay the concerns and issues of the Cult of Manann through Magdha and Frederick. This has caused further food panic and issues as even with the population of the Ark being reduced by fighting, treachery, explosions, and otherwise, actually getting access to what food locations remain has become somewhat more chaotic thanks to everything else going on.
Furthermore, this has meant that the remaining Dhar Anchorstones are under increased strain, as they have not received the immediate maintenance and repairs and stabilizing that they would normally require the resident sorceresses on an Ark perform if one is heavily damaged or outright destroyed. There are protocols in place for this, but they are not being fulfilled. The rest of the Coven remaining would really, really, really like it if Alyssa would stop demanding they find Hultressa and Gwendolyn, and would actually help them fulfill those protocols, or at least help them quell the dissenting nobility and other Cults of the Cytharai who are resisting them because if someone doesn't get on that soon it's going to be bad for everyone on the Ark. But currently she's spending her time torturing a single human because of how angry he's made her, and because he's the closest thing to Hultressa that she can find, meaning that the Coven is currently without her leadership. The Herald of Slaanesh is making motions towards taking command of things itself, and none of the Coven actually particularly want that, because the entire relationship has been spent more towards peer-ship and outright control and domination, not submission. No one is attending any arena shows, the arena slaves are currently less guarded than they have ever been, but getting to them is no walk in the park at the moment either. There are other slaves who are currently starting to head into the tunnels out of fear given the battlefield the above has become.
Hultressa isn't dead, but she did destroy a significant portion of the Tor of Dominance's innards in her anger while retrieving Gwendolyn, so that's not great either for control mechanisms of the Ark. She's also exhausted and beat to shit, so is laying low to recover, but does intend on trying to find the Handmaiden as swiftly as possible because she's hopeful that they linked up with the others. And then, with the others, they can try and go for Frederick as well.