Thats an interesting pitch. Those stories all make sense in isolation, but I feel like they wouldn't really fit with the game overall. Firstly, I think Selune instigating the whole thing would make her entirely unsympathetic and really ruin Shadowheart's story if it continued unchanged. Even ignoring the shadow curse that results from Isobel's death, Swlune is meant to be a good goddess and having her do something that intensely calous ruins that idea entirely. Shar doing something to make Halsin kill Isobel is better in tHalsin that respect, but in both cases it feels cheap honestly. Halsin has no agency, he was just there at the wrong time.
I feel like thats kind of the point for Halsin though. He diddnt ask for any of this, he got swept up in it, but he still wants to make things right and do his best. I really would have liked the oppourtunity to have supported him as he confronted his guilt and remorse, and work with him to help him lift the curse that has ravaged his home for 100 years.
And yea it would kind of mess with Sharts story if Selune did such a thing, but good gods arent immune to doing bad things it seems in DnD. Just look at what Mystra did to Gale, asking him to blow himself up. if you make Gale suicide bomb the elder brain at moonrise, which is what we are led to believe Mystra wants at the time, everyone infected turns into a mindflayer. This means Mysta isnt all knowing, and is willing to sacrifice someone who was so devoted toher, even though she is supposed to be 'good', just because she got angry. Gale may or may not have fucked up but I dont think it was reasonable for her to ask him for his life, and I would argue was a very bad and immoral thing for her to do, even though she is a 'good' goddess. But gods will god, people do their bidding and will because they are gods.
I would also argue, that Aylin being Selunes offspring, may influence Selune making choices she may not otherwise make. Because its her child involved. The gods in DnD seem to be suseptable to many of the things mortals are: jealousy, rage, etc etc. Maybe, with this, Selune made a bad choice. A mistake. Thats even assuming our characters even realize it may have been her. Maybe no one finds out.
But I still think the broad strokes are whats most important, the nitty grittys can be fleshed out better. Something happened, and it involves Shar and Selune, causing Isobel to attack Halsin, he kills her in self defense. And everything goes to shit from there.
