Well I might be completely wrong, but I suspect that chapter 3 will be about the fallout of what was setup and will be setup at the investiture of Sharon. Whether that will be completed in chapter 3 or will be a red thread for whole game is an open question though.
Astrid may well be the major antagonist that will be moving the forces against Sharon and MC in rest of game as Arigon thinks (I agree with him that Astrid is very likely way more as she seems, just not sure if that goes into the direction he thinks yet or completely different, I would not be surprised if she is much elder as she pretends she is and a bit tempestuous and likes to be visible while hiding what she really is maybe even an elder of generation 6-8 herself) or she and Marcius may just be the main antagonist of chapter 3 and she is no more as she seems.
Where we find out what the past is between Astrid and Sharon and that storyline will end in chapter 3 and another antagonist will take over in later chapters, where even C may well at a certain point be an option, especially if Sleeping Beauty is less related to C as we think or has opposing goals.
Edit: Just if Astrid is more as what she seems her interest in Sharon and her extreme anger and disgust for Sharon being unwilling to thread her corrupted path as shown to Gregor seems a slight confirmation that there is also more to Sharon as she seems and she may also have a lot more potential possibly. Who knows potential that was limited on purpose by Astrid by keeping her unknowing and unaware of older bloodlines and powers till she would be corrupted.