I have a feeling we are all forgetting a variable in this equation, Tyrande. I think Tyrande will end up being the Jailer's true weapon, not Anduin. Tyrande has all the same traits Arthas did when he was tricked into picking up Frostmourne. He had a lust for Vengeance due to what the Scourge did to his people, just like Tyrande has a lust for Vengeance after what happened to Teldrassil. Both made quick & rash decisions on how to stop their enemies, Arthas lied to his men & betrayed the Mercenaries that fought for him, Tyrande became the Night Warrior & Jumped into Hell just to Kill