I know that one villainess likes intrigue, and another likes handing magical tutoring to foolish young folk and seeing what they do (after they pay her). There will be characters who try to exploit this. There will be at least one for whom it backfired very badly, and the results are significant in the main plot.
Bit hard to see how to festoon them about the main tale evolving in the outline. Perhaps I shall just let them grow in the first draft, where I usually learn of them.