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Sometimes, I think we all just forget that Halt is in fact a huge fucking Nerd™. Think about it.
All the stuff he knows about history and culture and languages and geography, and just about anything he can get his hands on. It is especially mentioned in the first four books, like when Horace is trying to avoid a history lecture from Halt - and he is so familiar with them that he can tell just from the tone Halt is using that he's about to start one.
Halt just genuinely enjoys learning about the world around him, and I think that is awesome. It's nice to be reminded every now and then that Halt is just super smart. Tactics, cultures, food, plants, law in other countries - you name it and he probably knows a good bit about it. Even art! He's always the one to do artistic stuff (Shield emblems, writing out and making seals for documents (forged, obviously), making weapons and disguises and acting - whatever is needed, he's got it covered. And you know that if he doesn't know about something, he is sure as all hell going to learn.
Just wanted to bring that up, remember to incorporate things like that into writing, it's a pretty neat character trait that never actually gets touched on.