This box set expands the universe of Malifaux by adding the Order of the Chimera. The Order includes Marcus (leader), Myranda, Sabertooth Cerberus and Razorspine Rattler.
From the Malifaux Tactica Wiki:
The beastmaster of Malifaux, Marcus causes animals of all varieties and alliances to succumb to his will and follow him into battle. Little is known at this time about his background, but he helps the Arcanists and the Miners/ Steamfitters Union by his own means. Like the rest of the Arcanists he take his orders from Ramos.
Marcus is one of the few Masters who can hire Minions from any faction... as long as they have the Beast characteristic. He is a hit-and-run style Master, not doing a lot of damage on his own, but relying on his Beasts to do the heavy lifting.
Typically seen by many players as one of the weakest Masters in the game, but other folks contest it simply a matter of learning how to utilize him. He is certainly a fun and versatile Master to play, and if you decide to start a Marcus Crew, his wide choice of minions inevitably ends up encouraging you to expand to additional Masters, since you'll have the models to form the foundation of those crews.