Hmm I think the large Groups of summoned guardians must have been the problem. I killed three Groups of them and now the framerate is back in the green. I used the pause function a lot since that seemed to force a redraw of the screen (which only happened once every 5 seconds otherwise). The tower map is really cool btw. It seems to use a few different connection types, which is nice, it makes the map less precictable and gives a nice "what's around the corner" tension.
My fighter seems quite invincible right now with the loot he found in Lord Sertis layer. might have something to do with the fact that I used the spell-patch on the module. those berserker orks aren't that impressive anymore
. I also started as a level 1 character, which might mean that the monsters generated in the dungeon are of a somewhat lower level than they should be. still having a lot of fun.
I'm off to grab the Last key..