This video shows how the Quest is done. Do not forget your Destroy Field Rune when you want to pick up the Key 3610!
You cannot do this quest alone! The part which shows you how to get the key starts at 1:40. You need to pull the lever, kill the cyclops and use the Destroy Field Rune on the fire on the top left stones. Use the stones to get the key. Then go to Mintwallin and someone needs to stand on the sqm which is shown. This sqm will make the sewer gate visible and useable. Go down, through the level door, do not fall in the holes or you will have to fight a Giant Spider, watch out for the Dragon, open the door with your key, go down and clean the final room. The Dragon spawn is not the fastest (atleast 5 minutes) so if you swap positions with your friend standing on the sqm in Mintwallin he won't have to kill the Dragon again. Incase someone already did the quest and opened the door to the Giant Spider you will have to kill it aswell.
