Stone's Arena was the hardest part of entire game for me, even though I later played all of FOV. The big problem I had was that the Memory Eater sub-boss in the arena could one shot all 600 of my health with a single magic blast...
Even when I used summons that he would magic blast, I would have to get close and melee him to kill him since I was playing a warrior. At some point he would just turn and magic blast me and kill me instantly.
Eventually I just got lucky and one time he only magic blasted my summons.