... grab a grease bottle in the Ironhand gnomes cave in Rivington.
The room with Tulla had some rotten barrels that were white. (Contrary to all the red containers in the cave) So I looked into the first one, and found some grease bottles. Took them, no prob.
The second barrel, also white, also contained 2 grease bottles. I took them and all the gnomes became hostile and attacked immediately. Not even a choice to put them back or persuade them it was a mistake. No turning back. Had to kill them all. Including Wulbren and Barkus. All we did for him counted for nothing anymore, compared to a couple of grease bottles.