I think all interpretations of Mystra in Baulder's Gate 3 are valid and I'm not trying to take any away from anyone. Especially since stories of abuse and abusers can obviously be incredibly personal. However, I see people often painting her as either actively villainous and malignant or as the victim of Gale. Again, I think that's valid, but I see her as not quite in the middle - I believe there's no ethical way for a god to have a relationship with a mortal, like a boss or professor is always going to have an unethical relationship with a worker or pupil so she's still in the wrong - but still somewhere between the two extremes.
(Side note: I wish the game had in game books or something with more of the lore from DND that it was sticking to. They play fast and loose with DND lore (valid it's quite frankly convoluted), but Mystra and Gale's dynamic can be really affected by that. It would just give a bit of clarity.)
Firstly, like I said a god can't have a romantic relationship with a mortal and that be healthy. They will always have more power, socially, physically, etc. They have followers they can turn against you; you've heard about them your whole life and likely worship them; they can smite you. It's like trying to date Jesus there's no way for that to be normal. People literally thought for a while that Gale was wearing a matching earring with Mystra until they realized he was wearing the equivalent of a cross. However, that is still a reminder he wears of how as a wizard he’s irrevocably linked to her. That's why Gale is so insecure in game. Why he wants to be more powerful to be worthy of you. Why if you're in a relationship he's always asking what you need, "how can I help?" "Is something on your mind, you can always unburden yourself with me?" "Anything I can do for you, consider it most enthusiastically done". Mystra set an impossible standard that he was literally incapable of meeting and is haunted by.
Mystra is tricky with relationship dynamics because she has a precedent of not leaving all her lovers’ mortals. "Gale's folly" as he calls it, to be her equal, is not so wild an idea with Mystra. She helped the god Azuth become a deity and he was initially one of her mortal lovers. Although, Azuth isn't one of her lovers now and, they technically did not even become equals he is her subordinate. You understand where he got the idea however, and how he thought it could work. So, Gale is ambitious and arrogant sometimes, but I would argue wanting to be equal with your lover, especially when she's done that before, is not totally unreasonable.
I don't know beyond the power dynamic, how you have a normal relationship with a god, a god who is your everything and you're temporary for them. She doesn't need to eat so his other skill isn't important and likely uninteresting to her. If he tried to give her a normal gift, there is nothing beyond something as big as the Karsus Weave that another lover or follower hasn't given her a million times over or she hasn't seen and experienced as she watches over mortals. Like he probably can't tell her about a book he's read without her already knowing all about it, depending on how omnipotent she is. By being with her everything else falls away, until there's just magic, just her.
Gale says "I sought to cross her boundaries" which is certainly a charged statement. He absolutely did cross her boundaries and should not have. Even if I believe Mystra is more in the wrong two wrongs don’t make a right. I also think Mystra's appearance plays into this feeling particularly violating to some people. People like to joke about her looking plain for a goddess, but she does look like a regular mortal woman. Women have a reputation as more often being the victims of things like boundary crossing and she looks like a typical victim, not an all-powerful goddess. For example, if she looked like Shar I feel like people would empathize with her less. Which is a clever mechanic to make Gale’s story opaquer both in the text and non-diegetic interpretations. Both the writers and Mystra could be using her form to make her more unassuming and less blatantly other from Gale. So, I really get how people see her as the victim here even if I disagree.
On the topic of charged statements Gale calls Mystra his "teacher". Mystra holds the keys to secret knowledge. She will literally always know more than him. In a way he will never stop being her student. He does use the past tense to refer to her being his teacher though. So, she isn’t actively teaching him, but it does add an extra uncomfortable element in the imbalance of power that already exists. I personally believe if the Spell Plague is a part of the BG3 timeline (although it’s dubious since no one mentions it) she most likely only started actively interacting and teaching him as an adult. So, she was more like his professor than teacher which does have less uncomfortable implications. Ex-student teacher relationships have a predatory feel to them due to the age of the student initially. Thus, ex-student professor feels less fraught. This grey area around the nature of their schooling relationship is one of the many reasons why giving up the crown is such a positive ending. He becomes a professor and protects his students like she didn't protect him. I think it's also telling that in the epilogue if you play as Gale, you get a letter from Elminster, another Chosen of Mystra's, who tells you he has been your teacher since you were eight. Which is certainly uncomfortable. Whether Mystra was his teacher as an adult or a child an agent of hers was his teacher then. Beyond worshipping her thus she had even more influence in his life from a young age, even if Elminster taught him of his own volition.
Another thing that reminds me of abuse dynamics is that Mystra gets Gale alone and away from you. In the Stormshore Tabernacle Mystra does not allow anyone to accompany Gale for support. It just reminds me of how abusers isolate you. I'm pretty sure Gale even has dialogue about how being her Chosen was isolating and did not make him popular. Which you could argue is not her fault how others react, or that it’s Gale’s personality, but I find it telling paired with everything else.
As I've said the power imbalance is severe. It is not necessarily quite as bad as people describe it though. From what Wikipedia tells me Mystra can't take Gale's magic away from him completely, a thing people often site as a threat she has over him and part of her abuse. "Mystryl had ultimate control over all magic and could shape it to her will, and she could withdraw a being's access to the Weave and prevent it from using spells of any sort, and in an even harsher restriction she could also prevent a being from using any sort of magic whatsoever if she so decreed. These conditions persisted until she removed them.
Mystryl could even deny deities access to the Weave, but she couldn't deny other gods the ability to grant their worshipers spells through prayer." She stopped this though as it says. Which admittedly isn't a firm reassurance that it won't happen again- it would still worry me - but apparently it just isn't a thing that she does anymore. Plus, it can be interpreted that she also isn't allowed to anymore because of Ao (the head god) banning it as it would count as interfering with her godly portfolio. Thus, she's not necessarily quite as tyrannical as people worry.
Mystra is attracted to great spellcasters, such as arch mages, like Gale and Elminster. She specifically seeks people who are ambitious and crave power. Everyone's met a gifted child that turns into a mentally ill, burnt-out, average person when they're older, I would say I'm one. I would argue that natural talent or being a child prodigy, like Gale, isn't enough to get her attention or at least keep her interest. Even sorcerers would have to work on control. You need a certain level of ambition and drive to keep being greater. So, this is kind of Mystra's folly. To keep finding ambitious young men, give them the ultimate confidence boost with your attention as well as the ultimate temptation of magical secrets you keep and then get surprised that not all of them fall neatly into line like Elminster. As Minsc says "Now I wonder if it was not done to hide them from Mystra, and the snares she sets for young prideful boys, hm?" This isn't to say it's okay that he crossed her boundaries but again like I said she shouldn't have sought him out in the first place. Also, I, a neurodivergent person, see Gale as one too. I can't imagine someone dangling everything there is to know about my special interest in front of me like a tease.
Gale being tempted by the magic that he couldn't use is understandably vexing because before this iteration of Mystra he would have been able to. Up until the fall of Neverall all powerful enough magic users were able to do the magic she now hides. As her wiki says, "she laid down new rules for all spellcasters, banning spells above “9th” level, limiting who had access to magic, limiting how many spells of each level could be held in the mind, increasing the time it took to cast spells, and forcing long periods of memorization or prayer each day to replace spells cast previously." Karsus essentially went and ruined it for everyone so I get why Gale would want to be an exception to the rule. Mystra loves him, why shouldn't she trust him? However, Karsus did kill her, so I understand why this is a hard boundary for her.
Mystra is a god. She has a certain amount of distance from all mortals. She knows that all mortals die. As seen in her dialogue if you play as Gale and talk to her in the Tabernacle, she must balance the weight of many lives over a few. When asked if she cares about lives you might take if you explode, she says, "Such eddies are unexceptional. Souls arrive and depart your plane with every tide, in circumstances just and unjust." As a god you must have a certain amount of distance from mortals, it'd drive you mad otherwise. It's also what you want from a god. They should understand the bigger picture and not get caught in the weeds. Gods should not experience empathy the way mortals do; they'd get overwhelmed or go crazy otherwise. I see this otherworldly attitude of hers in Elminster’s line "She would consider what she considers to be forgiveness." Implying that she feels things differently, more inhumanly. Mystra is a good goddess but incapable of being a good lover because of this. So, she entered a relationship with a mortal who worshiped her with the knowledge that she could never reciprocate those same feelings back, there would always be a distance. Which is an obviously toxic thing to do, and she should have known better, Gale isn't her first lover.
Mystra being bad at mortal emotions and empathy is seen in other dialogue of hers at the Tabernacle too. She tells Gale, "You were already worthy. What you lacked was patience". What is she trying to say with this? You were worthy of being my Chosen? He knows that he already was her Chosen so that wasn’t what he wanted. Is she saying he was worthy of godhood? I doubt she was contemplating making him a god. There's no deep sorrow coming from her like someone who was thinking of sharing everything with him - if Ao would even allow that. I believe it makes the most sense that she believes he just wanted more power. That would make the patience line coherent. She thinks he just rushed into finding something to make him more powerful instead of waiting for her to grant him more power. Her Chosen can use greater powers like Silver Flame after a while. However, this demonstrates her lack of understanding of his character. He didn’t entirely want more power; he was planning on giving the tome to her. I don’t even think he was even aware it was something he could use. He thought it was HER weave not a separate thing of its own. He mainly wanted to be her equal. Gale isn't hungry for power for the sake of it. He always wants it for a deeper reason. He wouldn't have been content just following in Elminster's footsteps, being an incredibly powerful ex of hers one day. He wants her to love him with all the devotion that he has for her. He isn't with her for power, or at least that's not the main reason. You see it with your TAV if you romance him, Gale falls madly and quickly in love with people, love is all encompassing for him. He’s strictly monogamous he isn’t interested in sharing someone with others. He's not content to just have a fraction of her heart and give her all his.
Mystra's distance from humanity and how toxic these relationships can be is seen in the story of her possession of Elué and their relationship with Dornal Silverhand. Done to create the Seven Sisters to preserve her legacy. Being Chosen is not some altruistic thing Mystra grants to the best magic users for a job well done, or at least it isn't just that. They also become her insurance if she gets killed again, which is what these children were for too. She loves her Chosen but they’re also tools to her. She possessed Elué to sleep with Dornal (assaulting him I would argue as they make a point to not tell him about the possession) which deteriorates Elué. Although, I've seen people say that she's had a lot of bad relationships with mortal men, I haven't read the books I'm just going by the wiki and Wikipedia, but admittedly I can't see anyone she's screwed up quite like Dornal and Gale. Although, like I've said I don't think any close relationship she has with a mortal would be healthy. The closest I got besides them was Sammaster. However, from what the wiki says it's unclear whether his downfall was Mystra's fault or if that was just Algashon's manipulation to get him to blame everyone but himself.
I've seen people site that one way that their relationship is unhealthy is that Mystra is thousands of years older than Gale. Now depending on when and how she started interacting with him (this is where what I said about DND lore comes in, Mystra's death can change this whole timeline) this can absolutely be toxic. But an adult age gap, even thousands of years, isn't unhealthy I would argue. Once you reach maturity an adult's an adult. No one is up in arms about Astarion being 350. Also, Mystra maybe even tries to balance this. Her page on Wikipedia states that part of the power's her Chosen get is long lives, like Eliminster.
Gale reports in the Tabernacle that he's never been nervous before but in Sharess' Caress he says that he's insecure and even gets Tara to leave the room when he changes. I think saying he never gets nervous might be a bit of postering on his part, but admittedly that's totally up for interpretation (as it all of this is). From Mystra's wiki "As a goddess, Mystra could shape change at will and mortals who saw her reported she changed constantly". So, a man with insecurities and a person who literally never needs to feel insecure could be fine but with all the other points is just another reason Mystra should never have instigated anything.
Mystra states in the Tabernacle that she has been feeding Gale's orb with herself. She is the Weave. She has been feeding herself to this void so Gale can live. Gale was feeding on the weave in the magical items he consumed, thus unbeknownst to him feeding on her. He then continues to do this through the spell Elminster performs just more directly. As people have pointed out she could have helped him anytime. But this comes as a massive sacrifice to her. He did unleash something that damages and threatens her. He also unleashed something that is likely traumatic to her. From the dev notes from her dialogue, she is still angry at Karsus for killing her. The crown of Karsus is what allows her to control the weave in him. It's a different type of magic as she states, like Shar's Shadow Weave, one she can't control without the crown only feed. So, she couldn't have stopped the orb before he got the crown. She could only help Gale feed it. Some people say she could have cured him right away, but I don't think that's the case.
The Karsite Weave is dangerous. As Mystra says "You've unleashed something that would consume all magic in existence". However, I've seen people compare Gale's fragment to the Spell Plague, which I think is a bit much. If he was allowed to live and keep feeding off her, especially with a Chosen's life span then it could be. But Mystra need only send someone to kill him or stop feeding the orb and he will erupt, and it will be all over. She continues to hold all the cards.
I do believe she maybe could have prevented this all in the first place. Gale states that reading the Karsus book was like a flare going up to her, also that she hears every spell (Another issue that Gale must feel watched and scrutinised every time he performs magic). I don't believe with this power that Gale could have easily researched and found the Tome of Gateways without Mystra knowing something about it. His research likely would have shot up flares like when researching Karsus. If she knows every portal that he creates or spell he makes she should have known something. Plus, Gale's fine with charisma but not great and it's not like he's proficient in deception. Either she was paying him ridiculously little attention (and in the final product of the game they are together until he finds the Karsite Weave so it's unlikely that she was ignoring him) or she had her own reasons for letting him go ahead. Which does seem unlikely considering how awful Karsus' Folly was for her but if it's true then it is obviously toxic to let someone you supposedly love risk themselves and then blame them for everything about it.
I don't believe Gale was likely a minor when Mystra started a sexual or romantic relationship with him. For one, she was probably kind of dead, depending on whether her DND lore is canon or if Larian have fudged the dates. Also, Gale states that he's had previous lovers before her. Which could imply that she never actively sexually groomed him as a youth. Or that he had lovers then her all as a teen. I don't think if she was grooming him, he would have taken lovers while it was happening though, as he states she's "a jealous goddess". Her reputation could have partially groomed him though, worship from a young age of this beautiful woman surely influenced him. She also could arguably have been not sexually grooming him but grooming him to be her Chosen. Furthermore, I know some people use the term grooming for all ages, but Oxford languages defines it as relating to minors. I think if you want to use the term grooming for any age because it fits better for you VALID! But I haven't been groomed so I feel more comfortable sticking to the dictionary definition and just using the term manipulation for when he's older.
Gale, like I've said is flawed. For one he's arrogant and ambitious. If you leave him unchecked, he will become a god of ambition. However, it is not that hard to turn him away from this. I love how all the characters deal with their circumstances differently. It makes them all feel unique and human. If you compare say Astarion who is also power hungry to Gale you see how power isn't that big of a deal to him truly, feeling enough is (power also isn't Astarion's true want, its freedom, but I digress). However, Astarion has multiple dialogue scenes where he argues his case for Ascension and disapproves if you tell him outright that it's a bad idea (or at least I'm pretty sure he used to, with every update I swear they change the characters approval/disapproval). Whereas Gale gets you to the bottom of the bookstore and is like Hey, sorry I've been depressed but what if I was God? There's no manipulation here, he's not trying very hard beyond hiding his intentions till then. He can be talked out of it easily too. He doesn't disapprove if you tell him outright no. I did neutral answers, including telling him to do what he wants, and it still ended with everyone reacting like I'd convinced him not to be a god. He brings it up again at the end. But there's no persuasion role to convince him. You're just like No Gale and he's like Cool. His blasé attitude certainly doesn't scream power hungry. He does need a good influence though. Left to his own devices with no help from you he would go through with godhood. But it’s not like he doesn’t try to surround himself with good people, like Tara, and do the right thing.
Furthermore, he doesn't want to become a god just for power. He wants to feel worthy, to feel in control. He wants to do good and help people. Which is an admittedly stupid thing to think. Gale is the one to tell you in act one that the gods can't interfere Ao won't allow them but under the bookstore he apparently believes now he's just built different. Gale bounces between moods. He can be suicidal then want to be immortal. Overconfident then anxious and insecure. Power hungry then chastising you for doing the same. I think it reflects how his quest is the least black and white, he's still figuring himself out. But he's not a sweet darling who has never done anything wrong (like bragging to Loroakan about his upcoming godhood) or truly power hungry. With the evil pixie lamp, he tells you that he did it for practical reasons and disapproves of you wanting to do it for power. Similarly, he doesn't want The Necromancy of Thay except to consume and destroy it. I think Gale stands on a precipice between extremes.
So, to wrap it all up. I don't think that Gale is some scheming abuser. He's certainly not a perfect victim but you don't have to be to deserve better. Mystra in turn I don't think is trying to hurt Gale. She likely doesn’t understand the extent of the damage she’s doing. I don't think she can properly empathize with him. She's a goddess first and a lover second as she always has been. Knowing this she should stop having close relationships with her followers. It's a lonely existence being a god but that's the price you pay for that kind of power. Mystra is absolutely the abuser and should have known better but she's certainly not evil. At least that's my two coppers about it.