I cannot complete the quest, as the Demon is bugged and does not despawn, which causes multiple lvl 40 elite Demons to be stacked on the Quest NPC.
I have also already completed Shard of a Felhound and got the information, that I would not be able to hand the followup quest in because of that.
Is there any way the Demon will be fixed soon or for me to still hand the last Quest in?
RESOLVED: I was lucky that someone cleared the hut from the demons and I was able to complete the quest, could hand in the following quest just fine.
