This Gaius=Tetzel thing isn't new but the idea of "Rhue" being Gaius/Tetzel's "purpose" and the following quote I found in another topic, made me think of one theory:
Magnusblitz wrote:2. Who exactly IS Gaius? We know he's one of the Blood Lyn's attempts at the perfect dispenser of justice (sorry, I forgot the exact title), but why is he traversing around, killing people with Rhue before The Way begins?
In fact, the more I think about it, the more that scene (Rhue killing Jeruh) doesn't make any sense. Gaius walks up, and is basically like "you good? 'Kay." and leaves. Yeah, let's just leave the Shadow Sword there. Don't get freaked out when Rhue runs off by himself. And don't try to fix Rhue right away, either, despite the fact that you know something's wrong with him. Let him round around for six episodes instead.
The theory is that Gaius arranged everything
He supported "Rhue" in chasing Jeruh because he wanted to make sure that "Rhue" kills Jeruh and takes his (shadow) sword. Of course he was content when he saw that Rhue was succesful and walked off pleased. Gaius/Tetzel planned to
combine the 'Mimic' (the most dangerous being on the Way) and the 'Phantom Slasher' (one of the most powerful arms) to create the "Perfect Blade of Justice".
But when he discovered that the "PBoJ" tended towards getting outta control, killing chaotically, Gaius/Tetzel decided to destroy his creation (Beginning of Ep.6)