Start: Mansion south of Ardougne Castle
Requirements: 20+ combat recommended
Items needed: None
Talk to Ceril, then head south past Brother Cedric until you come to a Cave entrance. Enter the cave and talk to Clivet. Now it's time to choose the good or bad side.
Option A - Good Side:
Tell Clivet he's crazy and you'll never help him. Exit through the ladder to the surface. Now you must find five sewer valves that run along the nearby wall dividing West and East Ardougne. The proper configuration is: Valve 1 (near the purple dye spawn: Right, Valve 2 (northwest of Carnillean house): Left, Valve 3 (north of lever hut): Right, and Valve 4:, Right, Valve 5:, Left, which are both on the north end along the wall.
Go back to Clivet's cave and board the log raft. You will end up at the end of the sewer. At the hideout, talk to Alomone. This will automatically start combat, so be prepared. After defeating him. you will receive the Carnillean armour. Bring this back to Ceril. When the character is talking, he will accuse the butler of being one of the cult's members. The butler will deny the accusation and Ceril will give 675 coins to him and only 5 to you. Search the nearby butler's cupboard in the bedroom. You will automatically show the evidence to Ceril, and he will call the Carnillean guards on the butler. Quest complete!
Option B - Evil Side:
Agree to help Clivet and he will give you a poison for one of the family members. Go to the Carnillean house and put the poison in the cooking range downstairs. Talk to one of the family members, and they will tell you that their dog died. Go back to Clivet he will give you a Mark of Hazeel. Go upstairs and configure the five sewer valves (see Option A section for details).
Now go back to Clivet's cave and board the log raft. You will end up at the end of the sewer. Speak to Alomone. He tells you to retrieve a script from the Carnillean house. Head to the Carnillean house, and go to the basement. Search the crate down there and you'll receive a Carnillean Key. Head to the top floor and search the bookcase to end up in a secret passage. Use the Carnillean Key on the Carnillean Chest. Bring the Script of Hazeel back to the sewers and speak with Alomone. Lord Hazeel appears, restored to full power. He thanks and rewards you. Quest complete!
1 Quest Point
Thieving Experience = (Level * 57 + 205) x Custom Rate