The problem is that the tadpoles are largely just vehicles for the divine shadowmagic controlling them
Not sure if this is shadowmagic specifically as that is a whole other can of worms. Is that known for certain from early access or something? We know the dead three are working together and seem to have some kind of alliance with the illithids but for Shar to bundled into this alliance would be something else. We know Shadowheart is on a mission for Shar to take the artifact to Baldur's Gate but to suggest Shar is directly involved with the dead three and the illithids is something else.
We know this for sure from Ethel. (Not that Shar gave consent to its use per se, though. There's mixed messages, but her magic is in your brain. That's why Ethel can't remove the tadpole if you haven't checked that path. I'm just not sure if you're more focused on her plotting here than the magic).
