Alright, I still can't find a controller.
Slade
Slade's got some major emotional problems deep down. He was taught to respect and obey his mother without question. This makes him a sort of child-figure role so he clings to his superiors like they were his parents.
He has a relationship with Lexus, as we can see. It's mostly one of hate, but we notice that Slade saves Lexus at one point (in the Casino Basement) and he is honestly willing to protect her. I think it's a combination of both following orders, and seeing Lexus as the sister he's always wanted, and needed to protect so she doesn't end up like Chasta. At the same time, he dislikes her because she's disobediant herself and puts herself in danger.
Slade is the best person for Rhue to relate with. When you see them talking, you can see Slade is a lot like him, but more of a puppet than Rhue.
Slade's last big role is the showdown between Rhue and himself on Laodecia stretch where he gives Rhue a good thrashing and getting himself a good word-thrashing about how he has ability to stand up for himself.
Our vigilante almost gets killed and witnesses what he thinks is yet another death (Lyrra's). Because he's let so many girls down in his life, Slade becomes depressed and detatched from reality.
One of the last things he says before he jumps off that cliff is "I can't help you, I can't help anyone". Kloe approaches him and he gets jump and throws himself off. He wasn't really suicidal, but he was cornered by a girl, and he honestly thought that he was cursed to have women die around him (His younger sister, Chasta, Lexus, Lyrra), so he tried to save HER the only way he thought possible: By killing himself.
(Somehow) he survives the fall long enough to realize what a failure he's become. He thinks he can't save anyone, he knows he was a puppet. So just before he dies, he does one thing he knows is just and right for him. He stabs Cetsa and dies.
But really, Slade doesn't notice he does uphold a lot of justice for himself. He resisted Patura's advances because he knew he couldn't do something wrong, even if it was for his superiors. He confronted Rhue by himself without orders because he believed he was a criminal. So Slade wasn't a failure. He was just pessimistic as hell and believed he was.
Strata
Strata is THE Lyn. He's one of the best sword-fighters around and has a huge ego to match. I almost thought he was like Gary from Pokemon when I first saw him. He's pretty much Rhue's rival.
He doesn't play many roles until chapter 4, he just slows Rhue down, bugs him and causes him some serious trouble. For such a deadly guy, he's pretty petty going after a young nobody like Rhue. So Strata kind of has a inferiority complex. He likes to put others down because it makes him feel better. Why else would he pester one guy he met repeatedly?
Finally in Chapter 4 he becomes Rhue's biggest obstacle. Both Trazuin and Rosmar, two guys Rhue could never have a hope of beating, suddenly are scared of Strata. And Rhue realizes beating Strata is his only hope of ever freeing Cetsa. Things seem stacked in Rhue's favor, eh? Well, yeah. Rhue loses, and Strata humiliates him (He humiliated me, I didn't last the 6 passes. >_<)
Strata finally gets his just deserts when Traziun manages to make him humilate himself. Strata never won a fair fight as Trazuin threw it. This seems to piss Strata off as he can't be the best to himself if he doesn't beat the best fairly.
Cut to his relationship with Lyrra. He's completely using her, like he's using everyone he's fought. He knows her dad is dead now that Rhue tells him, but why doesn't he tell Lyrra that? On one hand, Lyrra may leave him, but on the other hand, Rhue will get his ass kicked by Lyrra. I think it may be the latter. He doesn't seem to care for Lyrra, and he said to Rhue "I'm not a bad guy, you know".
Cut to where they find Slade with a sword inconspicuously stuck in him. Strata is getting annoyed with Lyrra, and now that he knows her dad is dead, so she's just wasting time searching. And he still doesn't tell her. Finally he's fed up with the search and leaves her. He plunges Cetsa and wins, still using women. He needs trophy wife to rocket himself to stardom. Of course, "the wife" Lyrra learns this and grabs a sword (Can someone tell me why people think this is a Shadow Sword?). After all that trash-talk Scatha gave her, plus what he sees Strata doing makes he go crazy and she chases him hilariously across The Way.
Finally they stop by the rebel camp where Strata tells Lyrra the truth that Rhue killed her father, Rhue conviniently nearby. She charges Rhue, gets killed. Rhue leaves and Strata makes one big-ass revelation. "I see it all now". He left Lyrra right? She wasn't going to rocket him to fame anymore, so why did he give a damn? Because he did give a damn. Deep down, he cared for that crazy lady. Now he has to get revenge.
In the case that Rhue fought (and won) Strata is suprised. All he can do is sit there with blood on his face and stare. He's finally been beaten, and he can't take it.
What's in store for our friend Strata? I think his realization that he cared for someone coupled with his realization that he's not perfect will lead him to becoming a deeper character. If he doesn't become a deeper character, he's gonna get killed for sure. He can't face Rhue, so he'll have to join him or someone else, or just fade away (and I doubt that)
Serena
Not much to say, she's defined but why Rhue says. So either...
1) Rhue has a bad memory
2) We decide who Serena is (Unlikely, Lun sucks at giving us choices.
)
3) Serena is just an idea Rhue has and she doesn't exist. Serena is like his "perfect woman" so we define it by how we like women...or something.