this might be a bit spoiler-y if you haven't read the most recent book, lost stars. :U
i've been reading forum posts from when only the preview was released and for some reason people really wanted shadowpaw to be a villain? i don't understand that. we don't need more evil shadowclan members to make it an interesting story, i'm tired of evil shadowclan cats. but on the flip-side i really think shadowpaw might be something different.
like, he is obviously not getting his visions from starclan, and no other medicine cat (even ones like goosefeather) had seizures accompany their visions. my theory is that his seizures are due to these visions not being from starclan. no other medcat aside from him in lost stars has had any contact with starclan, and i think whoever is contacting shadowpaw chose a medcat apprentice for a reason... an apprentice wouldn't know the difference between starclan and whoever is contacting him now.
i haven't finished AVOS, nor read tigerheart's shadow yet, but based on lost stars and the knowledge he's had these visions since birth... when starclan was able to be regularly contacted, puddleshine probably saw him as a prodigy and took him as his apprentice, but it was never starclan contacting him in the first place. i feel like shadowpaw wants to be the best medcat he can be, but whoever is talking to him in lost stars is actively sabotaging that.