I have recently beat him. With only weapon, it's nearly impossible to get over 5th stage the 2nd time. You need to be well prepared for it, especially with potions and some extra damage. Here is mine. At the 5th and 6th stage, cast spell whenever it's recovered, especially lightning. If you don't have lightning, you can use dancing sword ( can't remember its exact name LOL) with meteors. Further info is included. May the odds be in your favor :)