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Marcellus is Luka’s father and indirectly stated to be Heinrich’s descendant. He had slain Alice XV (Fifteenth), the previous Monster Lord, along with Lazarus, Karen, and Merlin, but realized her intentions for coexistence too late. Just as he and his companions were proceeding to spread her wishes, Alice XVI (Sixteenth) came along and attacked the group out of blind rage upon noticing her dead mother, killing Karen and Merlin. Having killed Karen, a woman whom Marcellus and Lazarus both loved, they founded Ilias Kreuz out of vengeance.
However, when Marcellus began assisting monsters by sneaking out to them and informing them of the Ilias Kreuz’s plans so that they could escape, Lazarus felt that Marcellus had betrayed both the ideals of the group and insulted the memories of Karen and Merlin. Lazarus executed him and spread the rumor that monsters killed him so that a further wedge would be driven between humans and monsters.
Luka was originally aiming to become a martyr because of what he had heard and been told, holding the belief that Marcellus was a crazed terrorist and that he in turn would be required to die to correct the sins committed by his father.