Marks Spencer is a high-ranking officer within the Chevalier military organization, serving as an under-secretary and the director of the Evolution Pandora (E-Pandora) Project, an initiative designed to turn ordinary human beings into Pandoras. He is a harsh and determined man who runs any operation under his command with an iron fist, and he is notorious for taking on controversial assignments and playing the role of a villain for what he believes serves the greater good. His commitment to the mission often leads him to act ruthlessly, and he will not allow anyone to interfere with his plans.

Little is known about Spencer's early life, but it is revealed that his significant other, a Pandora named Hilda, died fighting to protect mankind. This personal loss may have hardened his resolve and contributed to his pragmatic, sometimes cold approach to the war against the Nova. He became the adoptive father of Charles Bonaparte after rescuing her from a life on the streets, a relationship that shows a more caring side beneath his stern exterior.

In the story of Freezing Vibration, Marks Spencer serves as a major antagonist. He is the primary figure behind the E-Pandora Project, which is unveiled at the Chevalier's Alaskan base. His involvement with the project and his questionable methods eventually lead to his apprehension following the 11th Nova Clash. As a character, he does not possess any special combat abilities; his influence comes from his authority and political acumen within the Chevalier hierarchy. His role highlights the moral ambiguities of the organization's fight against the Nova and the lengths to which its leaders will go to secure victory.