Originally Posted by Darak
If I remember correctly, I believe you also have to purify all of the other Shadow Pokémon in order to get Fein to appear with the Togetic.
That's not how it was for me. All I had to do was catch all the other shadow pokemon. I haven't managed to purify them all yet, but I still was able to battle Fein...
Thanks to Astral Shadow for the button!