I think it is the child inside cordy. You know, the one she got when she bonkered Connor. I think the kid might be some evil god and is secretly (and at a subconscious level) manipulating cordy. Way back when Conner was still in Darla’s belly, there was a prophecy going around way back that angel’s child or some such will bring about the apocalypse. Everyone thought it was going to be Conner. But who knows, maybe Conner is merely the intermediate step.
Of course, I could be totally off.