So, I'm not great at coming up with stuff. Fortunately for me, I had a couple of things happen that naturally created storylines.
The first was that the party explored and found the Dark Lady really early on.
At that point, they didn't really know what was going on.
So she offered them information in exchange for a promise that they'd give her any orbs they found.
Which allowed me to basically dump the Background section of the book onto them, as well as (once they got their hands on an orb) creating this ongoing tension of "Is it really a good idea to give these this thing to her? Can we get away with not giving it to her?"
Er, oops, they only promised to give her the first orb they found.