Duneon called mithering descent

I got an blue market dungeon on the top of the map called mithering descent, at the end of that dungeon is an enemy called sodden effgy corpus of the wight, i cant kill it. What is this dungeon good for?

It is an area used during a quest chain, that started in Northshore around Marowen.

So what i have to do? Or is this another bugged dungeon?

Iam not new at this game, alrdy hit lvl100

Its bugged dungeon, there is topic about it here in forums

I would think if you can see the marker, that you’ve already done the quest. But, not sure about that. I just did the quest a couple of days ago, and it worked for me.

Edit: In looking at my map, I see that it is the only quest dungeon that still shows after the quest is finished, so in that way, it is bugged I guess.