We don't know who the Harbringer is in Ep. 5. Then I had a thought.
Firstly, what do we know about him?
1) He was hired by the Guided
2) Rhue can't hit him
3) He was going to kill Cetsa
Now, this is the way I see it. Why would Gaius help the Guided? He doesn't to be particularly into them... which leads me to believe that he wanted something off of them. Like Rhue, he joined a gang so he could gain access to Cetsa, but he had a different purpose in mind...
We know that the only two people in the entire series that Rhue can't seem to hit are Gaius and the Harbinger. This suggests some sort of connection between them. Assuming that Gaius has the Illumanati sword, Rhue's Shadow Blade wouldn't be able to hit it. That explains that. So, either the Harbinger had the Illumanati sword at that time (unlikely) or he is Gaius (more likely) or he has some sort of protective spell.
Why would he want to kill Cetsa though? Well, it boils down to two things in my mind; either Gaius is so obsessed with making The Way pure that he wants to kill her himself, or the Illumanati can absorb auras like the Shadow Swords. The first one seems far more likely, as we have never heard any tales of the Illumanati absorbing auras.
There is also the way that Gaius found out Rhue had a Shadow Sword. He had fought beside Rhue before, but never commented on it. Only AFTER Rhue attacks the Harbinger and Gaius teams up with him later does Gaius say anything. Why would he wait so long? Surely the longer he waits, the more auras Rhue absorbs and the more unpure The Way becomes.
Your thoughts?