I don't know if this is intended or not, but I'll report it as a bug since I think it's lame the way it currently works.
When turning in 'Helm of Balduran' for Degrodel he disappear instantly.
This is not fine, if I play a backstabbing no-gooder I should be able to turn in the quest and then be able to try to kill him for the helm.
The fact that he is just gone is quite immersion breaking too, he could drink a invis. potion, cast invis, cast dimension door, invis. contegency (I don't know his level he probably ain't high enough for contegency). Just something that can be believable.