Originally born in West Virginia, Mark Simmons made his way to New York City when he was still a teenager and joined the Ingues Cartel as hitman, becoming instrumental in their rise throughout the 80s and 90s. After a dramatic power shift in the cartel, Mark left and worked on his own for a few years, though he still retained some connections to the cartel. Finally, he happened upon a Shop operation by chance; some confusion and a few bodies later, Dr. Lothario Algernon officially recruited him as an Archer asset in the final months of the conspiracy. Mark managed to survive the Archer downfall and hooked up with Equinox, taking over much of the operations of the newly founded American wing of Fagin's Umbrella.

Mark just a "plain old human", but well-trained and blessed with a lifetime of experience. He combines expertise with a wide variety of weapons (though he prefers semi-automatic pistols) with an almost eerie ability to zero in on the weaknesses of his targets and exploit their shortcomings. He likes to project a simple, "loveable rogue" personality, goading many people into underestimating him.

Physically, Mark is a larger-than-average caucasian male slightly past his prime, with dark hair and brown eyes. He's frequently slightly unkempt and prefers wide clothing to conceal his personal arsenal. He almost always carries two H&K USP Tactical .45 pistols on spring-loaded rails in his sleeves, allowing him to draw the guns with a flick of his wrist.