If I had to sum up my primary ally’s arc, it is similar to Han Solo’s from A New Hope: He goes from being a self-absorbed rebel (though with a soft spot for my hero) to accepting responsibility and his place in the order. His background is different, of course, so the reasons for his desire are completely separate, but that is the best comparison I can think of for his character change.
His character arc also sets him at odds with my Guide, so that should result in some interesting group dynamics as the story goes on. I did not see that coming at first, but I think it will help keep the story amusing and engaging in the middle parts.
With my ally’s primary arc complete (I am also considering a romantic subplot for him, but nothing strong or overt – I hate it when romance gets in the way of the main plot), my next step and possibly final character arc is for my Jester character. So far, she has been the least related to all of the other character’s arcs, to the point that I worry that she might not really have a place in this story, so I have to craft her arc carefully to make her essential. I intend for her to play a more significant role in the sequels, so I do not want to eliminate her.