Marcus is one of the villains from Blood Omen 2: Legacy of Kain.
Marcus was one of the vampire lieutenants of Kain, who had started a coup to take over Nosgoth. Kain didn't trusted Marcus, believing he wanted to betray him. Kain tries to kill him, but Marcus manages to escape and hides himself. Marcus believed that Kain was actually afraid of his powers. When Kain is defeated by the Sarafan Lord, Marcus betrays the vampires and sides with the Sarafan, having his life spared and starting to hunt down all other vampires for the Sarafan.
When the two meet again, Marcus taunts Kain, saying that he is now more powerful than him. He attempts to mind-control Kain, but fails, although he did managed to see Kain's thoughts, discovering that he was after the Bishop of Meridian. Marcus then challenges Kain for a race to see who reaches the bishop first, leaving him to face some mind-controlled humans. Kain reaches the bishop, but discovers that Marcus is already controlling him, chasing him to the rooftop of the cathedral. The glass ceiling didn't supported their weights, making the two fall into the altar, where they fought.
Marcus becomes invisible and attempts to attack Kain, but he sings the bells of the place, stunning Marcus so that he could attack him. Marcus summons more mind-controlled humans to help him, but Kain ultimately prevailed, killing him.