Who is Slidell and Mason from The Monstrumologist and what is their importance?

Slidell and Mason are two confederate supporters who, working with Alistair Warthrop, pay to bring the Anthropophagi to the United States, initially to mate with humans in a an attempt to cross breed the species. Slidell and Mason were wealthy, and helped to fund the entire experiment, hoping to create a race of super human-killing machines.