Nightmare was relatively easy. I was level 7 when I found a level 15 imp but what killed me was a Shape battle. Can't stand those. Could You remove the shark like enemies that follow you?? At least make them slower. I find them to be the hardest enemies so far and the main reason I lost the shape battle. Also perhaps You could add arrows to the battle tutorial to show where is something, I was lost for a while looking for the buttons. Also, I think the life bar for the scarecrow should not replenish that fast, for a moment I thought the attack spells were not working.
All in all I liked it.