It's experimental in that it's content scales depending on the difficulty you select and the loot drops will change to reflect that.
Talk to Pumpkin head in North Karana and he'll help you find your way into Miraguls Nightmare! The instance for each difficulty is open so have fun grouping and raiding up with your friends, plus there's new items to loot, but be warned, these nightmares won't give them up easily!
As mentioned the code that makes this work is new so please let us know any issues and also let us know how hard or easy you find it
