[Azaghal]

Thank you Lord ( I had to do this blasphemic thing once). Your hint was a good one. As soon as I opened Mulaheir's chest with the letters still in my backpack, it started the cutscene. Doubted your advice first because I thought the completion of the quest and thus the beginning of the next chapter was connected to the mayor of Nashkell (and he was already gone in my game), but you saved my day.