[bsftcs]

I think one can steal everything that a monster or an NPC can drop when killed.

There are some items that will only "materialize" when a certain quest is completed. An example of this is of course the assassin's dagger which will only "materialize" in Scanthril's inventory when the quest to kill Raskalion has been completed (and undertaken first). Other examples are the key and the vampire's ring which will first "materialize" in Adrianna's inventory when she has received the scroll of banishing. If one kills Adrianna before retrieving the scroll she does not drop these items.

Then there is of course the possibility that some of the items of this sort are "quest" items. Killing the trigger triggers the action, and killing a person carrying a quest items prompts his or her dropping the item. Although I have never confirmed it via an experiment I think there may be items that will only "materialize" when a certain quest is completed but at the same time are quest items and will therefore "materialize" and drop to the floor when the holder has been killed. But these items cannot be pickpocketed. Perhaps this might be the case with Kreug's key?