Gamasutra reports that Ensemble Studios was working on a now-cancelled MMOG based on the Halo universe at one point, theorizing the game was internally cancelled last year without ever being revealed to the public. They have a screenshot of a level and another showing a prototype of the planned UI for the game, along with some analysis of what it reveals. They also point out that comments by Microsoft leave open the possibility that such a project is now underway at some other studio, recalling Microsoft's Phil Spencer recently mentioning: "There are more than two or three teams building Halo things right now."