Lets get something straight. Shaidar Haran is not Moridin. He is not some ressurected forsaken from the age of legends. He is a f***ing myrrdraal. (Here is my idea) :I believe that he is the dark one himself. Shaidar Haran means 'Hand of the Dark.' It is mentioned that Mydraal's powers stem from the Dark One himself. So, it would be logical for the Dark One to break free partially. If you noticed, when the first seal broke, Aginor and Balthamael were freed. When the second and third seal broke, so were the rest of the forsaken (Remember Lanfear's sudden appearance in Falme). When the fourth seal broke, then the weather began to change, and Shaidar Haran was introduced as a character. Coincidence? Maybe, but I think not.