five months after the Beastwoman had been touched by the Sylvaneth, she died, with no trace of her soul left.
So, that is moderately concerning, but I don't think jt's quite reason to go running to the Inquisition just yet. Here's my thought about what happened.
The Sylvaneth are some kind of Eldar (or maybe even Old One) experiment on how to purge Chaotic Corruption from the souls of others. At some point, they were lost or forgotten about. And when that Minotaur ended up in close proximity to one, it did what it was 'created' to do, which is purge spiritual corruption from other beings. However, due to it either being an unfinished/abandoned project, or not having experience with human/human-like souls, the process accidentally removed something integral to the self-sustainment of the woman's soul, thus resulting in its eventual degredation and her death.
So, depending, this could still be a hugely useful resource for us, just one that will require some fine-tuning to understand and work out the issues with.
The Inversed God-Emperor. Death from afar and from the Warp.
The Candle. Something will light the way.
And the Sword. From war it will come, to war, it will go.
This, I think, is a good indication that it is
something to do with the War In Heaven, or at least its participants.