I have to go with the Djinn simply because it was great to take him down on Hard Mode with no ancient weapons or promotions - crazy I know but going on without a clue of which way this 1hour!!! battle would turn out really made my day!
I like it when boss battles are long and equally balanced on both sides!
I agree with Dee with her view of things on Thanatos and Ozur but for me Thanatos even with just 3 party members was not so hard due to my excessive levels - turns out that's a side-effect from thoroughly searching for secret rooms!
I guess now I should try taking down the Gripphin with no promotions and Piu-Piu in my party!
