Bross leads the antagonistic Dark Joker, dedicated to eradicating all universal life. An incarnation of evil and destruction, he orchestrates his schemes from an ever-shifting orbital palace, deploying the Black Vaccine—a corruptive substance spreading disease and rot—to annihilate the Flower of Life. This vital entity fuels the creation of the Green Vaccine, his opposition’s sole defense. By destroying it, he aims to secure absolute dominion over Earth and its mirror counterpart, Queen Earth.

His leadership over subordinates like Dewey and Keto is marked by ruthless pragmatism, with internal power struggles and betrayals fracturing their ranks. Bross callously discards expendable followers, exemplified by Dewey’s abandonment and subsequent rescue by protagonists. Unbound by loyalty, he resurrects fallen adversaries such as Kanon, brainwashing him into a weapon against Nurse Angel Ririka—a tactic highlighting his exploitation of emotional bonds to weaken enemies.

Exclusive to the manga, Bross shares a familial tie with a younger brother, Regi, omitted in the anime. The anime concludes his arc with Dewey—now allied with Ririka—destroying the Black Vaccine’s core vessel within his palace. Yet residual traces of the pathogen perpetuate his influence, prolonging the conflict. Conversely, the manga resolves his defeat decisively, restoring peace without lingering threats.

Across all portrayals, Bross embodies relentless annihilation, devoid of remorse or moral nuance. His schemes culminate in a climactic showdown where adversaries thwart his plans, though remnants of his actions endure. Without personal backstory or motives, he symbolizes pure destructive ambition, an existential force opposing life itself.