Having just gotten to this stage myself, I want to clarify: placing and building Greselda's Castle does NOT unlock the Adamant Alchemy Quest Line. I had to complete her castle THEN collect from it twice ("Visiting" her castle twice is the final part of that segment of the Greselda quest line, "Specific Taste") before the the Adamant Alchemy Quest Line appeared.
Also want to add a big THANK YOU to everyone in this community who posts all the stages of all these quests for folks like me to research and prepare ahead of time for things.