To get this key, first zone to Castle Zvahl Bailey. Once inside you will need Sneak and Invisible or Sneak Oils and Prism Powders to avoid the aggro from the Eyes and the demons. After entering follow the path till you come to a cross and take the right path heading north. Follow this path till you come to a ramp down enter the ravine and head left/ South, make sure to stay to the left when you come to a junction this brings you inside the castle.
From here head to the left/ North if you continue North you will come to a corner and a ramp along with a large hole in the ground make sure your Sneak and Invisible are good and walk into the hole. There should be Demon Commanders, Chancellors, Generals, and Magistrates, these drop the Whine Cellar Key that you need. There is a hall off this circular room where you can set up camp. These mobs are 55-59 so a full party of 52+ should be ok if they are careful with their pulls. I went with a 60 mnk and another 52 blm we had no problems even with a link, except when one demon got freeze off. I believe that there are 5 demons in the pit and one that spawns behind in the hall we killed them all 3 or 4 times for 2 keys which would be a drop of 1/12 or so.