Mylanor was a lord of the Winter Elves and a commander in the first years of the war that broke the Crimson Coast kingdom in two. The records that survive do not agree on which claimant he served, Lamenrae or her uncle Taoinor, and it has stopped mattering. He was killed somewhere in the northwestern highlands, violently and carrying a grievance, and his body went into the water that his kind would give its name to.
He did not stay dead, and he did not stay down. The River of Wights runs through country where the First Dark drains slow, so the violently dead pool there and rise on their own, with no necromancer to call them. Mylanor's shadow rose carrying more than most. It kept the cold cleverness of the lord he had been and the reflex of command, and the lesser wights along the upper river move when it moves them. What it does not keep is Mylanor. The self that bore the name faded to Celestia at his death, the way every self does. What gives orders now is the spite of a dead man wearing the shape of a living one's authority, and that is worse than a haunting, because it can plan.
Both halves of the broken kingdom understand what a captain who cannot be killed a second time would be worth, and both have failed to take him. So has Chaal Nazzerox. The necromancer-state sent one of its better thread-binders, Vazreth Sythrox, up the river some years ago to clamp the wight-lord to a proper leash. The leash never closed. Mylanor felt the Deoric working reach for his shadow, turned it back on the man who cast it, and left him dead on the bank with his life-price already spent. The river raised Vazreth the way it raises all its violent dead. His shadow stands among the lesser wights of the upper water now, taking the orders Mylanor gives. Mylanor holds his stretch of the upper water and answers to nothing. That is the difficulty with him. He is a standing officer with no king left to recall him and no caster to dismiss him, and he has all the time the dead have.