When blasting the cave-in blocking Nere with a satchel, a large fire surface is created. When Beldron (Ironhand's Steward) comes running out he moves through this fire surface and takes damage which cases all of the Duergar to aggro. This is quite clearly not what is supposed to happen. The NPCs should not path through a damaging surface and if they do it should not cause aggro.
The satchel was placed on the ground then exploded with a Firebolt spell.
The one time I did this with a fire arrow instead, no aggro was generated although I do not know if the NPC pathed through the fire. That particular playthrough ended up freezing in the dialogue with Nere without crashing.
