The sword summon spell the prisoner starts with is good, but pebble works too. You can be sneaking and get the meterorite staff and boulder toss for this fight, but I did not need it on my newly minted sorcerer play. I was able to beat it at around L20 with the prisoner startup, using wolf summon and Rogier, with no issues. The big trick is to never get greedy and always keep enough stamina in reserve to roll the fuck out of the way, especially with phase two hammer attacks. If you really want to make it easy, get the shackle from patches.