Ok, everybody who DIDN'T see it coming that I would have to start a thread like this for Jabal as well, raise your hand... get your hands off the floor, you doofs!
Anyway... my impression of Jabal so far:
He's, as mentioned, very talented in combat, and probably in strategy and tactics. He's highly intelligent, and curious, hence the fascination with the library. However, he's also cocky/arrogant - I've yet to see him acknowledge that he has any limits at all. I know he's supposed to be young for his position, but his cockiness makes him seem younger still. I get the impression that he's not a very mature 25 - he seems like he's emotionally more like 17-20. Basically, in D&D terms, high intelligence, not so much on the wisdom.
My suggestion for planning: It is obvious that he and Luther are good friends. Think about what it is about Jabal that makes him a good friend, as opposed to just a challenging sparring partner... at least if you want Jabal to be a likable character. Right now, I, at least, am sort of neutral on him. Basically, he seems a smidge annoying to me, but I'm willing to reserve judgement, for Luther's sake, since Luther likes him, and I'm starting to like Luther. (:
Upcoming enlightenment
Jabal's redeeming qualities should come to light fairly soon in the story. He's got very strong convictions regarding liberty and morality, and is also fiercely loyal. We'll soon find him parting ways with Luther over a conflict between their duty as soldiers and what Jabal himself (and Luther, whatever he may say aloud) believes to be the correct course of action. Though not without leaving Luther with something to think about, of course.
Sounds potentially interesting....
Looking forward to watching this character develop!