There is too way to start and complete this quest, however, both ways have the same difficulty to complete (but I'll will warn you now: this quest is so freaking easy...).
- First way
- When you reach dungeons level 4 back to town and talk with Odgen. He will say something about noises on the night and some shadows that looks like monsters in town. When he wake up, his sign from the Tavern of the Rising Sun was missing. He will simply ask you to find it and bring it back to him.
Back to the dungeons and seek the stairs to level 5, you'll find a unique Fallen One demon called Snotspill guarding it. Just go through the door on the other side (close to the stairs). Kill those "fat dudes" that guards the sign. Grab it and take it to Odgen. He will thanks and handle you the unique item: Harlequin Crest. When you back track to the dungeons, talk with Snotspill and he will open the way to the stairs together with a horde of Fallen Ones. Kill them easily and continue your jorney.
- Second way
- Instead of talking with Odgen just talk with Snotspill, he will say something about a "magic sign" that has been stealed by that "fat dumb dudes" and only will let you go through if you give it back to him.
Make the same thing you did on "First way" guide and grab the sign, but now, handle it to Snotspill and he will betray you and set free the way together with that Fallen Ones' horde. Kill them all easily though and make your way.
Curiosity: if you talk with Odgen first, but handle the sign to Snotspill, when you come to talk with Odgen again he will thank you and make a joke about that "magic sign". And will regret about his lost sign.
Tip: giving back the sign to Odgen will handle you a better item than giving it to Snotspill.