Yes, Carol Berg is very much doing A Thing. The Lighthouse Duet was the first of her books that I read, and I think maybe the Spirit Lens was the most recent, which may be why I like it less -- though also I felt like the series did not stick the landing, with my memories of book 3 mostly being *have we tortured Portier enough? of course not, this is Carol Berg!*. I liked book 2 the best of the series; book 1 felt unsatsifying because I could tell there was another twist to the mystery plot, and was hoping Portier would figure this out, but no, it was left for book 2.

Ilario de Sylvae indeed! :-D