Below is simply my conception of said viking. Above that is a scene of Erling dealing with his anger in a non-murderous way. Erling is a Christian Viking; as a result he's often at odds with traditional Norse culture on a number of subjects. To deal with the inevitable rage, he walks alone at night to the shore and hurls rocks into the surf. That is where the book's protagonist (an Irish Priest) finds him.
By the way, I'm trying to work in a different style here. Rendering figures with lines is much, much faster than painting them. It's an elegant style really.