This was one of my favorite episodes, as well. Now that we've established (maybe) who is real, and who is not, this episode showed that Shadow King (in all his forms) is in charge of all these people that have chosen to gravitate towards David. I'm not familiar with the comic, so these people's motives for clinging to him, I'm not certain of. I'm sure it will become clear, eventually. It seems that of all these people only Syd and Oliver (maybe Walter, also) have not been 100% controlled by King. What is clear is that for the story to advance to the point that David will actually be able to use his powers in any meaningful way, King the parasite will have to be eliminated, or at the very least, controlled. I think Syd being able to "see behind the curtain" is going to be key here. King being able to hijack David's mind whenever it wants can't be good unless the story's goal is to keep David institutionalized, and I don't think it is. Maybe they'll trap King in Oliver's ice cube.