The Addiction quest in Oblivion Remastered is part of the Understanding Madness storyline in the Shivering Isles. Here’s the walkthrough.

The Oblivion Remastered successfully brings back the magic of the original Elder Scrolls IV, alongside all of its DLCs. The Shivering Isles is one of them. While you venture into this expansion’s land, you will come across the Understanding Madness storyline. The Addiction quest is a part of it, and during it, Sheogorath will ask you to look for the Duke of Mania.
To complete this quest in Oblivion Remastered, follow this guide.
How To Complete the Addiction Quest in Oblivion Remastered

As we discussed earlier, during the Understanding Madness quest, Sheogorath will ask you to look for the Duchess of Dementia and the Duke of Mania. These two will be separate missions, and if you choose the latter, the Addiction quest will start.
Now, to find the Duke of Mania, you will have to go to his palace in the land of Mania. His name is Thadon, and you will be able to find him inside the building. When you talk to him, he will ask you to get the Chalice of Reversal, a special item, first. However, this is where the quest gets a bit tricky because the Duke won’t tell you where the item is.
Now you must seek out an NPC named Wide-Eye. She usually stays inside the throne room or near the Halcyon Conservatory. Wide-Eye will tell you that the Chalice you are looking for is in the Dunroot Burrow, and you will have to take Felldew before going there. The place itself is located northwest of the Mania palace, away from civilization.
Retrieve the Chalice of Reversal

Once you arrive at the desired location, you will spot an Elytra enemy near the door immediately. Fortunately, it carries Felldew. So, defeat it, take the Felldew, and eat it. It is necessary to enter the cave.
Inside the cave, keep moving deeper while defeating more Elytras. They will keep providing you with more Felldew, which is essential for your survival inside the dungeon. Eventually, you will come across the door to the Sanctum of Decadence. Go past it and then take the staircase. Then, you will have to confront some more enemies. Once they are defeated, you can simply take the Chalice of Reversal from the pedestal there.
After that, simply go back to Duke Thadon. Hand the Chalice over to him, and he will make you a member of his court in Mania. This concludes the Addiction Quest in Oblivion Remastered.
Looking For More About Elder Scrolls Oblivion Remastered?
Thank you for reading the Guide. We provide the latest news and create guides for Baldur’s Gate 3, Enshrouded, Dune Awakening, and more. Also, watch Deltia play games on Twitch or visit his YouTube channel!