Simple idea really. A housing item like Pagoda or Winterbane but with a random twist. 4-5 levels, each level being a random level appropriate boss fight based on the lowest level in party like other gauntlets. Requires no real work to make because it uses only existing content and drops. You never know what bosses you'll face or what order. You might be fighting Hades or the Sand Squid, maybe Morganthe or Belloq... could be Undying Malistaire... It would be a fun mixup of farming bosses without ever really knowing who's next.