Mack Hawthorne revealed
I asked an artist on Fiverr to create an image of Mack. Here is how I picture Mack and tried to describe him to the artist. It's an info dump. In the book we learn more about him as we go.
Malcom "Mack" Hawthorne
Mack is a former army sergeant in an era similar to the late 1800s. He is in his mid 30s and has a heavier build from years of physical labor. His square face shows the effects of a hard life, spent mostly outside. While he might not be in uniform anymore, he's unwilling to let his guard down. He survived several harrowing battles and has lost many friends in them. Because of this, he hyper vigilant and is normally armed.
Mack is extremely protective of his friends and anyone he feels is being taken advantage of. The experience of losing people over the years has made him quick to react when it feels like someone is in danger. This is something his friends admire, but it also worries them. He reacts immediately when a situation presents itself. If he feels he can prevent it, he will make the attempt without thought for himself. This has caused him trouble more than once.
Mack has been hurt both physically and mentally by his time in combat. He's largely healed physically, but the psychological wounds are still raw. He tries to hide it with humor, but there is a darkness to him. He has an anger that seems restrained by a very weak leash.
He's a good man, but he has a long road in front of him. Coming home is not working out like he had hoped it would.