In TGH, Rand tries to take the ways to Toman Head, only to find MS guarding the gate, waiting for him. Verin said:
"No-one knows exactly what Machin Shin is, unless, perhaps, it is the essence of madness and cruelty. It cannot be reasoned with, or bargained with, or talked to. It cannot even be forced, not by any Aes Sedai living today, and perhaps not by any that ever lived. Do you really think that Padan Fain could do what ten Aes Sedai could Not?"
Although Verin was protesting that Fain could not possibly control MS, I think that she gave us the clue to why he could. '...the essence of madness and cruelty.' and Fain is both mad and cruel. Further, in EOTW Fain said he communicated with MS in the ways, and Moiraine said that as soon as it enveloped him, it fled. Still further, people have been suggesting that MS is connected to Mashadar. Now, we know definitely that Fain has been merged with Mordeth, the counsellor from doomed Aridhol, and that he holds the dagger that Mat took out of SL. Also the glossary says that the amalgamation of Fain and Mordeth has powers that neither man originally had. Put all these elements together, and you can see my theory emerge. Finally I don't think Rand will face Fain/Mordeth. Or if he will it won't be for a while. Why? Because of the dagger. I don't think Mat and RJ have finished with the SL dagger. Also a few more things of interest... If Fain does control MS, does he also control Mashadar? Also, has anyone else noticed that Fain cuts himself with the dagger, and nothing happens to him. How is he going to die? Poetic justice says he will die by the dagger, but if it won't harm him, how's he going to be killed? I know I've taken a while, but I'm finally finished. Please make a response so I know what mistakes I might have made.