Brimstone emerged as a denizen of Jungle Planet (Animatros), becoming one of Scourge's primary acolytes during Scourge's rise to power and enforcement of order through dictatorship. Within Scourge's entourage, he functioned primarily as a temple guardian and aerial scout, frequently operating alongside Undermine. Brimstone exhibited limited intellectual capacity, consistently preferring to follow orders over engaging in independent thought or planning. His motivations centered on enjoying simple pleasures like combat, flying, and maintaining his position as one of Scourge's enforcers—a role granting him opportunities for violence without consequence. During quieter periods, he and Undermine often played Praxus Fold 'Em, wagering Energon goodies and chores. Throughout the conflict involving the Cyber Planet Keys and the black hole threat, Brimstone participated in Scourge's confrontations against Autobots and Decepticons. He witnessed Megatron's sparring match with Scourge and later engaged Autobots like Overhaul and Backstop. When Optimus Prime arrived on Jungle Planet seeking the Cyber Planet Key, Brimstone openly mocked Prime's initial reluctance to fight. He guarded Scourge during training rituals and observed Prime's subsequent victory over Scourge. Following this, Scourge retained leadership of Jungle Planet but aligned with the Autobots, an allegiance shift Brimstone followed. As the black hole crisis intensified, spatial turbulence triggered environmental catastrophes on Jungle Planet. During a massive monsoon, lightning struck Brimstone mid-flight, sending him plunging toward a lava flow until Backstop rescued him. This prompted Brimstone to reflect on whether he would have an opportunity to repay the debt before the universe's potential end. Later, when Galvatron targeted Jungle Planet with the Omega Lock's power, dark energy tendrils pulled the planet toward the black hole. Amid the cataclysm, Brimstone saved Undermine from a similar lava-fall incident, delivering sarcastic comments about Undermine's weight during the rescue. He escaped the dying planet aboard the Hyperborea with Scourge and other survivors. In the final battle against Galvatron, Brimstone and Undermine confronted the enlarged Thunderblast, though their effectiveness was compromised by their insults toward her. Following Galvatron's defeat and the sealing of the black hole, Brimstone assisted in constructing planetary thrusters to return Jungle Planet to its original orbit. In the post-war period, he witnessed Scourge reaffirm his leadership by defeating Leobreaker in a championship. Likely at Scourge's request, Brimstone joined the Space Bridge initiative aboard the Lemuria under Metroplex's command, representing Jungle Planet alongside other survivors. Brimstone transformed into a robotic Pteranodon equipped with diamond-edged vanadium wing blades. His Cyber Key activation (code d0h3) deployed spring-loaded blades from his wings in both beast and robot modes. His capabilities included silent flight and high durability, with documented attributes emphasizing speed (9.5), endurance (10), and courage (9), while his strength and intelligence were rated lower (5 each).