isnt this when you enter the tower after flying with fishy and kill the clockwork knights and enter the room of catherina?
Yes indeedy. "Magic barriers" == "Clockwork knights". My main difficulty was working out what I had to do to survive long enough when the demons were attacking. If the OP managed that, the next part is, um, feasible. I won't say that it is easy, but it isn't impossibly hard either.