The Dark Jedi Order were a faction within Universe V1.0.
The Dark Jedi leadership formed a relationship with the Night Jedi Order, and it was decided that the Orders should merge. The factions were merged under the Dark Jedi name, and Night Jedi facilities opened up to Dark Jedi members.
The Night Jedi heard nothing more from the Dark Jedi, excepting a few weeks later, when a rumour that the Dark Jedi had disbanded got through. Some Night Jedi facilities then reformed under the Night Jedi name again.
There have been rumours of the Dark Jedi Order having formed once again.