Characters come to life on the page. Readers know this as they experience the novel, but on the other side of things I’m always delighted when a character naturally evolves. Ajax arrives in Winter Begins to give Winter and Thad a push in the right direction. He was originally envisioned as being rude and funny, but not particularly deep. But once I began writing and he interacted with Winter things took a turn. He mattered more. His past mattered. And he has the ability to change the course of the series.
Jax grew enough to even get his own song on the writing playlist. If you want inside his head, listen to this one.