There are two issues that I want to blather on about in this article. First is the "use" of Allen and Van as devices for development of one of the themes of Escaflowne. The second is about Folken's character and his place in the series.
In the last several episodes of Escaflowne, we have begun to see the show's theme or moral lesson. In episode 26, Isaac's ghost explains it quite directly. People cause war. Those who desire conflict, those who hate and want to kill, cause the death and decimation that is war. Van and Allen are both this type of person.
More and more in the final episodes, this becomes all too clear. Hitomi begs Van not to kill for the sake of her protection. Just watch the bloodlust flare in Van's eyes when he enters battle! The first time we really got a good look at Van's vicious nature was when he brutally slaughtered Dilandau's lackeys and Escaflowne turned black. At first, I thought that the aftereffects of being drawn into that ghostly world would change Van's attitude. However, when Allen told Hitomi that all warriors go through a trial where they learn to deal with killing, he didn't tell her the outcome of those thoughts. The altering of one's morals and thought patterns to justify objectionable past actions is a well-known psychological phenomenon. Van begins to enjoy the killing.
In Fanelia, while meeting with Folken, earth dragons attack, but they seek only Van, for he carries the most rage. Folken proves also that a heart at peace can overcome this when he stops the dragon and Van. Still, Van pays no heed to his brother nor to Hitomi, both of whom urge him to remove himself from conflicts.
In the last episode, Van's malice reaches its peak as he kills soldier after soldier. It all culminates when Van and Allen fight (as seen in the opening credits) just because they enjoy it. Can Van finally understand why killing and war are wrong before he is consumed by his own fury?
Folken Lakur de Fanel, inventor of the stealth manteau and once heir to the throne of Fanelia, it can argued, was the true main character of Escaflowne. I'm not up on my literary criticism and analysis studies (and grammar), but I think that a fair case can be put forth that Folken is a tragic hero. His story is told through Hitomi and thus is mixed in with her own a bit, but it's all there.
Folken knew from the very start that killing is wrong. We are shown this in flashbacks to Van's childhood. Folken took up the dragon hunt to prevent that responsibility from falling upon Van because he didn't want his innocent brother stained with blood. Unfortunately, Folken, lacking bloodlust himself, was maimed. Then the dragon, sensing Folken's kind heart, left him alone once he was... disarmed. After being picked up by Isaac and learning to deal with his "new parts", he comes to believe that a world without anger and fear can be created with fate-altering devices.
He rescues two young catwomen from racist humans and raises them with love and kindness. Surely he is not a bad guy. His attempts to explain the truth to his younger brother is met with the cold stone of Van's heart. Eventually, he learns that Isaac's moral disposition isn't exactly coincident with his own. In the end, he resolves that he must kill Isaac and himself by consequence of reaction. He even says that he is exchanging his life so that Gaea and Van will have a better future. Truly, Folken is the hero of this story. Well, he's my favorite character, at least.