[The Sour Slig]

*potential spoil*

If the Prophets are actually Forerunners, then that would explain why the patterns of it's yellow thingies on it's head match many objects on the Halo. But in fact, the prophets are indeed the leaders of the covenant but the similarity of their yellow head thingies and the structures on Halo does leave room for questions and an interesting plot tie in.

Remember that 343 Guilty Spark mistook Master Chief for a forerunner...