The Elder Scrolls IV: Oblivion Walkthrough Part 6: Sabotaging the Secret Mystic Dawn Meeting

In the last part of The Elder Scrolls IV Oblivion walkthrough, you had started to collect volumes one through three for the book of the Mystic Dawn. Once you have all of them, you'll be able to decipher the location of the gang's hideout, and after obtaining the third volume, you agreed to take the place of Gwinas at a meeting between him and a gang member to obtain the final piece of the key.

Before you run off to uncover the secret, you first need to go speak to Baurus. Head towards the Boarding House and enter and exit the building to find him standing to the left of you in The Elder Scrolls IV Oblivion. Tell him about your meeting and he'll agree with you to go and get the last volume together. It's finally time to go get and the last piece of the puzzle, so make your way beneath the Imperial City following Baurus into Sunken Sewer.

Upon arriving at your destination, you'll be given two options being to either sit at the table alone or stand at the top of the stairs and watch for him to arrive. It does not matter which you choose, because either way the person on the stairs will be spotted by the fellow assassins and it'll be a fight to the death. So you've taken out all the enemies including The Sponsor, so check his body and you'll find Volume 4 in The Elder Scrolls IV Oblivion. One other thing you'll need to grab is the Sunken Sewers Key found on one of the assassin's bodies. Now, you're going to need to exit Dynari Amnis' Basement and you'll have to lock pick the door in order to get out.