38 seconds into the "Character Development" video shown at GDC, there is a brief image of a mysterious figure, clad in a hooded black cloak, antlers, and holding some kind of 'staff.' If the five panel "mood board" from the GDC presentation is anything to go by, then this figure may very well be a member of the as-of-yet unseen fifth race of enemies (possibly named the Glimmer?). This seems a plausible deduction to me as the yellow tone, black smoke, and white-faced black figure parallel the fifth image in the "mood board" quite nicely. Also (and this is a thinner comparison), the triangular shapes in the yellow "mood board" panel are similar to the triangular "ships" seen in another piece of concept art revealed at GDC (one that Bungie won't talk about yet), and the antlered figure's cloak does have a rather triangular hood...