So the theory I posted back on the RWBY thread, not using spoiler tags since I'm assuming anyone who searched out for this thread has already watched the show:
So King Harrow dies in the attack, right? But what if that wasn't the case. We never actually see him dying, much less how the conversation between him and Viren played out after he said Viren should be on his knees. So I'm sure a lot of people are assuming Viren killed Harrow before the attack, but I think many are forgetting about the two headed snake Viren brought with him and left behind when he confronted Callum. Remember what Viren's original plan for Harrow to survive the assassination was, to swap his soul into another body so that the Elves would believe their mission succeeded. But that brings up the question of who Viren switched Harrow with, well who ever said the soul exchange needed to be between two humans? Viren put Harrow's soul into his bird, Pip. What really made me have this erukea moment was when Viren asked if the bird had a song to sing, and the animal looked away. Now I recognize that this is fictional and the animals tend to be smarter (see bait), but that was a very human gesture, plus why keep the bird caged when it was shown to have it's own stand before? Now this revenge works on a multitude of levels. Not only does it force Harrow to watch as Viren takes his throne, but think about what Harrow called Viren, a servant, so now Viren turned Harrow into something lower than that, an animal.
Now to address the "bonded ribbon", all I can really say is that we don't exactly know how elf magic works, it could be keyed to either the death of the body or death of the soul. Now I'm going to assume it's death of the body because it seems like the humans have dealt with the elves before, specifically calling them out as Moonshadow Elves. While Viren is a vain man, there is no denying his intelligence and I highly doubt he would propose a plan that he knew would end in failure.