Bronach is a lhiannan shee who seems to have something to do with the Gauntlet and the Sentinel. Black Abe O’Shaughnessy intimated, at one point, that Bronach was the fey creature that constructed the dual artifacts in the first place. This seems unlikely as she isn’t powerful enough to have produced one, much less two, artifacts. Moreover, the purposes of the two artifacts (the defense and attack on Alderweg) are so obviously designated to separate forces that it seems far more likely that the artifacts were produced by two independent and opposed groups of magical artisans.
That being said, Bronach does seem to be personally invested in the drama of the characters’ plight. When the characters entered her Trod lair, known as the Vernal House, she was throwing a party celebrating the bearer of the Gauntlet. There is no indication, however, that she involved with the Fey smokescreen of the Three Very Fine Gentlemen (four if you count the Satyr). Black Abe seemed at odds with her, and the characters were given the impression that Black Abe was pretty much acting in accordance with the rest of the Fey world (he was welcome at the trial/his plans involved Dig, Dig, Dig). If she wasn’t involved with that drama, then Katrina’s turning into stone probably wasn’t Bronach’s fault. Which brings up the compelling question of what she has to do with any of this…
What seems obvious is that, as a dark muse, Bronach was, at one time, the muse of Red Tam and that she has something to do with his magic Rebeca (it was buried with him, but appeared again in the Vernal House). Her current artiste/thrall is a bard by the name of, although how well he’ll serve her when she can’t dangle the rebeca in front of him is anyone’s guess.