Narfinsel lies west of Imperial City, in the same general area as Gottlesfont Priory. It is a white stone building with a dungeon underneath. The ruin is inhabited by imps at lower levels and strong mythical creatures at higher levels. There are a few good chests of loot also.
In the far eastern room, there is some sort of trap mechanism. When activated, tall walls spring from the floor and trap you between them. They will lower themselves and go up again fairly quickly, so be ready when they go down. There is a glitch in that room as well. If you step onto one of the walls as its going up, it will shoot you up above the ruins. You can see the level below you along with a purple area (out of bounds). If you jump into the purple part you will not die; you just pop back up again somewhere near where you fell. NOTE: Do not jump when going up the wall because it will shoot you up too high above the level and then you fall down and will most likely die.