Lacklan Walker is a freelance agent.
Well, that is the best short description I can come up with but he is not, really. Freelance would indicate he does what he does for different contractors and that isn't true. He does it for personal reasons and to heck with anyone who would like to call the shots. Now "agent" would imply he was trained for his job, rather than be an amateur, and that is definitely the case though here again it would not be accurate to think it was by some Intelligence organization.
In the facts about the man, I list his nationality as British but in truth he is also American. It is from his father that he gets U.S. citizenship while his mother provided the British one. Though when we first meet him he is living in the western part of America, he had only recently moved there after spending over a decade serving in the U.K.'s elite Special Air Squadron.
Walker is around 30 years old when the series starts and he has tried to put his violent past behind him. About that previous life he states, "I was a killer, and I had devoted my life to becoming one of the best in my trade. I had risen with honor through the ranks of one of the most lethal regiments on Earth. The British SAS."
As for why he is alone and liking it when we meet, that can be explained through another statement, "Am I bitter? Yeah, I'm bitter. Sometimes people ask me if I have lost my humanity. I tell them, not yet, but I'm working on it. I don't like humanity. I don't like people. There is the odd exception, but that's what they are - exceptions. That's why, when I came home to the States after ten years, I moved to the most remote, unpopulated State in the Union. Wyoming."
He will not stay there long, much to his dismay. A call from his very much estranged father, a man he totally despises for reasons explained in the books, brings him quite reluctantly back to Boston and the mansion had reasons to hate. It will be there in that undesired reunion that Walker will learn about Omega and what he learns will give him a new purpose - to destroy it.
According to his father, a man who knows about Omega because he was a member of it, it was "A very special kind of club. You might say it was unique. It was a group of some of the most powerful men in the world, who decided, after the chaos of the three world wars, that the destiny of the world could not be left to random fate." Dear old dying dad added, "Democratically elected leaders, puppets!, pray to powerful and greedy industrialists rich enough to buy senators and even presidents. No, it had to be guided, and guided where we wanted it to go." And where it wanted the world to go could not in any way be considered good for the people who lived on it.
But there will be a personal reason for Walker's new quest. Marni. The beautiful woman he grew up with, loved deeply, and then chose to abandon. She, too, has learned of Omega's existence and she has an even more personal reason for wanting Omega destroyed. Unfortunately, Omega now knows it and are after her and to keep her alive, Walker must go to war.
One interesting observation that Walker makes early on is that he operates "based on the principle that you can never have too many weapons or too much ammunition." Considering the power of his enemies, a wise adage.