I managed to beat the group and loot the katana when my party was at an average level of around 10. I then went to De'Arnise keep, defeated Improved Torgal and brought the average level of my party (which consist of my Berserker/thief, Minsc, Keldorn, Jan, Aerie and Kelsey) close to 11.
I encountered the Katana stealing Kensai (dont remember his name) as soon as I came back to slums from the keep. The maniac is crazy hard - has about 5-6 (?) attacks a round, keeps casting protected from magical weapons, stoneskin, mirror-image and the like, has high magic resistance, Acid Backlash which fires a Melfs Acid Arrow when someone does manage to hit him and what not. He keeps going straight for the mages (jan, aerie and kelsey) first and my tanks are not able to touch/backstab him
Am I at too low a level to beat him? Will he still attack me if I do not have Celestial fury in my inventory? Any ideas/clues to defeat this guy would be a great help would be a great help. Thanks in advance