Syryth and Orin
(And all relevant context)
Technically, this is a tag game (thank you @moon-bliss-bg3) but it's an official lore post to me. I'll be back to fill in links later, because this is even more to tackle than I thought and will be multiple posts.
Warning for mentions of grooming and sexual assault.
Syryth, diverging from the game's canon Dark Urge, is approximately 150 years old (born a fair bit after the Great Bhaalspawn Crisis, for consistency). He moved into the temple at around 15, after he'd killed his adoptive family, and spent a very long time functionally alone. While he was technically under the tutelage of Sarevok, and had a lot of worship surrounding him, he didn't truly have someone he was close to. For many decades, Syryth's life was spent learning to be and subsequently becoming the leader of the Cult of Bhaal, as well as making his own personal sacrifices to his Father.
For the first 10-or-so years of Orin's life, she was raised in near-total isolation by Sarevok (a control which intensified after she killed Helena). She was essentially built to be the perfect servant to Bhaal, but constantly reminded to be humble and grateful, in ways that ranged from demoralizing to fully abusive. She was also raised with the idea that she might bear Bhaalspawn one day, and it was emphasized to her how she was in a "perfect position" to do so as a changeling. As she matured, Sarevok placed additional sexual emphasis on her body both in her original form and when forcing her to take different forms, “training” her to one day bear bhaalspawn or sire them within someone else (for the latter of which he employed victims for her to “practice” on.)
At 10, Sarevok felt it was appropriate to "debut" Orin as a visible member of the cult's leadership, and gave her to Syryth as his charge. She was elated to have more freedom and power, but was very aware of the strings attached, and had been told at the outset that she was going to be secondary to him functionally forever.
He found the idea of her being around irritating at first, and generally regarded her as immature, especially due to her unique mannerisms and sense of humour. However, as they continued to attend their duties together, this shifted. The first point of connection was how effective she was at killing at such a young age, despite going about it in a very different way from him. They fell into a rhythm very quickly, and Syryth found her prodigious at choosing victims and covering her tracks, something he assumed he would have to manage. They started to get along well in conversation, and Syryth's less serious side basically developed because of her. He never quite treated her like a child. They had strong rapport and unique banter with each other, including a laundry list of nicknames.
Syryth and Orin became extremely close. They were never seen apart unless by absolute necessity, and became incredibly insular in their relationship. The dynamic between them had become more equal as soon as they started getting along, but by the end of the fifth year or so, it began to take an even more drastic shift, at least in private. First, in Orin’s early teens, they began a sexual relationship. It felt natural to Syryth, who had led her through everything else, to help her through the urges that someone going through puberty often has.
By the time she was in her mid-teens, to a certain degree, Orin began to recognize that Syryth (though he would never voice it) found being the de facto leader exhausting, and Syryth recognized that Orin hated always being in second place. Syryth also developed the belief that, due to their shared blood, Orin's soul had always been with him, and that with her naturally vibrant personality and deeper connection to mortals, she was a more natural choice for 'the face' than he was.
Syryth loved Orin’s art, and let her use his body as a canvas frequently, usually shallow cuts that were hard to detect as to not draw suspicion. The climax or culmination of their relationship in this stage was when she took nearly a full day with him on the altar to carve the runic circle of Bhaal into his back, working slowly and in layers to make sure the scars took. It was a symbol of his devotion to Bhaal, but it was also a symbol of his devotion to her— two things that were increasingly becoming the same to him.
Ten or so years following this, in the midst of their full-fledged relationship, Syryth started to experience vivid visions and intrusive thoughts that he believed were a calling from Bhaal himself, telling him that there could only be one Bhaalspawn, and he was meant to cleanse the world of everything. (This was, in fact, a delusion of an unknown source.) It made him start to subtly pull away from Orin, and got him plotting.
Syryth had already made a lot of inroads and political moves involving the cult, including finding people with connections to the leadership of Baldur's Gate (among other places) to figuratively get in bed with. One such individual was the ambitious Enver Gortash, with connections to both the Hells and supply chains in the city. They crafted the Absolute plan together, had a bit of casual coworker sex, and began to set it in motion with their journey to the Hells and recruitment of one Ketheric Thorm.
All of this was a secret from Orin, a person Syryth had never kept a secret from before, let alone one this massive and devastating. Additionally, he was spending more and more time away from her. Following his delusion, he began to convince himself that the very things he loved about her were flaws; her artistry and her personality were reframed as unserious to him, and he started to antagonize her over them frequently. He started being more patronizing, emphasizing the difference in their ages in a way he'd never done before, switching out "blood-kin" and phrases like "my ravenous jewel" for the cutting "little sister," and if he was feeling particularly venomous, "young spawn" or "half-spawn."
As this deterioration happened, Sarevok expressed that they should have children together, as a way to strengthen both the Bhaal line and their connection (and for Orin to fulfil her 'purpose'). One of the only things they agreed on at this time was that he could go fuck himself.
Orin did a lot of digging to figure out why this shift had happened and what Syryth was up to. She was extremely confused, hurt, and especially angry. Even if Syryth had come up with the same plan earlier in their relationship, she wouldn't have struck, but their relationship had deteriorated to the point where she was emotionally able to seize the opportunity to harness the Absolute for herself. Her plan was never to kill him, but it turned out that she functionally did kill the Syryth she knew, and had once loved.
