I just noticed some interesting things in Marek and Lothander quest.
The quest begins in the market area only if you met them in area AR0300 before. Here you can kill both and block that damn quest. If you kill only one of them the quest is broken too, but you will lose the magical items of the survivor. If you attack Marek before his dialogue he turns hostile and you can defeat him withe ease. Lothander will remain there neutral and than you can kill him too. If you attack (and kill) Lothander Marek will go on with his dialogue and I don't know if there will be future problems/bugs.
The quest begins in the market area only if you met them in area AR0300 before. Here you can kill both and block that damn quest. If you kill only one of them the quest is broken too, but you will lose the magical items of the survivor. If you attack Marek before his dialogue he turns hostile and you can defeat him withe ease. Lothander will remain there neutral and than you can kill him too. If you attack (and kill) Lothander Marek will go on with his dialogue and I don't know if there will be future problems/bugs.