I have to say that it was really nice to see a nice theorised timeline of "Rhue", and I agree on a lot of the different stages of his life. (Though the question of "How Midian gets killed" is entirely irrelevant).
The only stage I don't agree with is the first. There is better evidence supporting the idea that "Rhue" is Venge. I say this only because (and many people seem to ignore this) but Rhue feels at home in caves. This is mentioned twice (by my count) in the series. The first time is in the cave in Episode 1. Traziun and Gaius are complaining, and Rhue? "It's not so bad..." The second time is in a thought to himself after Scatha discusses the 'merits' of the Under Way. "(You kind of understand what she means, don't you?)". The darkness is home to him, and fills him with a certain sense of nostalgia. I admit, that these are vague clues, but you have to work with what you're given.
Now, for the rest of this post, I'm going to assume that Rhue's original form was Venge for the above reasons.
Rhue's bodily form never changes. Ever. No matter how many auras he absorbs. He always looks the same. If Rhue is Venge... Why does he look so human? Well, is it that far of a stretch to call Rhue a child of Janwen's bane? By all evidence, the people of Janwen apparently had pretty close ties with the Reaches. It's quite possible that some residents could've even interacted with the Lord of Below. Venge could've very well had a human mother, while still having the Lord of Below as his father.
Now lets assume that the poem titled Venge is more accurate than Sacrifa. Venge could've rebelled against his father on his own, without the help of "heroes". Rejecting evil, Venge searches for an Illuminati and strikes his father. He doesn't succeed in killing him, but does succeed in scarring him at least. Nevertheless, the shadowed depths he once called home is no longer safe for him. His only protection is on the surface. And in a rage, the Lord of Below obviously wants to kill his son. He burns Janwen to the ground. Venge somehow escapes, and by escaping the Reaches *and* Janwen, he escapes the only real places his father has power.
Of course, while on the Middle Way... Confrontations will occur, one way or another. *THIS* is where he becomes the Mimic. And from this point on, I agree with the rest of your theory, Requiem.
Now the question that this does not answer is why does an absorbed aura replace Venge in the first place? The case of the Mimic seems to be a very special one that only involves a single wielder of a Shadow Sword/Illuminati, and in this case, it's our dear "Rhue". So allow me to theorise again, (though I admit, the following will appear even *more* farfetched than the above).
"Rhue", or Venge, is a half-breed. He is part demon, part human. It's pretty damn safe to say that demons don't have souls, and thus, no auras. It's safe to assume then that Venge (or "Rhue") was born with a soul (which led him to rebel against his father in the first place). An aura can't produce a soul, anymore than a shadow can produce an object. Since he's not entirely human however, he might not entirely have a complete soul, or maybe he might just have a weaker projection of his soul (aura) due to his lineage. Thus, the Illuminati first absorbing a strong aura might very well overwhelm Venge, causing the phenomenon known as the Mimic.
Therefore, while in Jopoga's laboratory, when his soul and his aura were both separated from "Rhue"... What was left? His demonic side, which has no aura or soul. This same ever-present demonic side is also what leads him to this violence. Even if his soul isn't evil, violence is in his blood.
As for how the Phantom Slasher came to be... Well, he was birthed by absorption of the aura of the lunatic murderer, Jeruh. Of course, Jeruh was just an ordinary murderer. There was no supernatural side to it (unless we assume that his descent into madness was caused by the sword he used in Landorin). However, that mentality combined with a half-demon wielding an Illuminati could just very well produce something sick and twisted enough as the Phantom Slasher.
So my revised order is this:
Venge -> Mimic -> Kura -> Kava -> *** -> Midian -> "Rhue"
Where *** means any number of individuals in between. It could be Kava... It could be somebody completely different.
- The two shadow figures, from which Jeruh gets the Shadow Sword. Going by the current read out, one of them would have had to be Kava. As something to note, could the second horrible incident that occured at Landorin, as mentioned in the Wanderer's Guide Book, have been the slaughter of the entire Guided Camp by Kava?
There's not much reason to assume that the person we know as "Rhue" has anything to do with those two figures. Nothing *really* ties him to them. As for the other Landorin incident... Yes, that's entirely possible, and very likely if everything before that is to be considered true. If the Illuminati that Venge wields has the power to absorb entire LOCATIONS, then it's entirely possible that the forest in Dream Estrana is none other than where the first massacre took place. Which, does in fact explain who the witch was. Kudos to you!
- When was Traziun's mom killed during all this? Perhaps, when Jeruh lost the sword, someone else picked it up before Rhue got it back again? Because as far as the current time line goes, none of them would have a real motive to kill her.
By my timeline? It was during ***. No reason to believe that any known or established personas would've wanted her dead. Therefore, it must be an unknown one, which must've occured not long before Midian. Incidently, this is why I believe that there were other auras between Kava and Midian. Neither would've killed Traziun's mother...
Well, that was long! Thanks for organising the Rhue theories.
PS: Now that Venge no longer has the Illuminati, not only does it lead to the demise of the PS and the Mimic, but it would seem that our pal "Rhue" is once again able to age and die. He can live a relatively normal life.