I did not get the Iron Butterfly at the Black Hole. I finished and graduated, now I can't figure out how to get back to the Black Hole to get the last butterfly.
Let me see if this helps. I looked it up, and the iron butterfly is in The Hive near The Black Hole. I read that you don't need to go into that dungeon, but from a picture I saw, you might want to look around if you don't see it, it looks like it would blend in. On the map, it look like it's to the right of the Black Hole area on your map.
