Haven't read the series in so long that I've forgotten most of the characters... The only one I remember is the main character's sidekick woods goblin guy with the bow, whose name I don't remember. XD So, yeah, I'd have to go with that dude.
Favorite side character... probably the gnome. Though maybe Krom. There are a good many to choose from. Caulder was perfect.
Too sad to pick Caulder, so I'm going with Beyan. He's got some good depth, I think his backstory will come into play at some point. And I like that he is a great example of Richter keeping his promise to help his villagers grow in power. With the Bodaks and the fact that he is the only known death mage in the village besides Richter, I think he will be a key member of the varsity squad for the foreseeable future.