Someone said that the trigger was concluding any one of your leads about getting rid of the tadpole.
It could be Nettie, Halsin, the hag... Or whatever else is there as an option, can't remember.
Also, I got him at my very first long rest, but that's probably because I rest very rarely in general so I had already played a significant chunk of content by then. People who do it after every single minor fight probably had to wait few nights before seeing him.
I can confirm that. for most players he comes after Nettie since she is the most likely lead people pursue first. I skipped her and tried the GIthenki guys and he appeared only after encountering them. It seems like a relatively easy thing to fix - make him come after finishing two or three leads instead of one
