Originally Posted by Harlequin
"Black Sovereign items can be found in Dimensional Boxes in Abyss dungeons in the Saintís Haven area."
The pass for hell mode is from the silver chest that appears after beating cerberus abyss, it's a 100% drop for each player in your party (if its the same as SEA).
You can easily solo abyss if you're properly geared. Hell on the other hand poses a bit of a challenge, 2 of his skills could shave off about 15-20k HP (the fire/ice AOE). The black lightning skill is easy to avoid and makes him vulnerable to your attacks that takes some time to cast.
I died twice on my 23k HP acro in hell mode and only got this:
(my first run in hell mode)