Curiosity compelled me to re-run the mission to find the exact relevant wording: "And one more thing- I've heard that some kind of force of nature had once tried to right his wrongs but Lord Vanaduke imprisoned it somewhere within his fortress. Finding and freeing it may prove useful."

So it would seem safe to assume the being in question is indeed the sprite serving as the Spirit Mother's proxy in the Charred Court and so forth. The topic made me skim over other Almire-related characters, and I am still wondering whether Chancellor Brandell's "final order" was what I suspect it was (a "you'll never take me alive~!" moment) or whether it was something more interesting. :o