Ren Krawler is a Gundalian Darkus brawler and the last descendant of the Protectors of the Dark Bakugan, charged with preventing his partner, Linehalt, from unleashing a forbidden power. His Battle Gear is Boomix, and he later commands Darkus Frangzor and its Titan form Zoompha, Rapilator mobile assault units, a Doomtronic Battle Suit, a second guardian Bakugan named Darkus Crownite, and a Gold Megazord BakuNano. Hailing from the underground world of Gundalia, Ren and Linehalt were isolated by Emperor Barodius's family because of Linehalt's dangerous abilities. Sent to Earth disguised as a human, Ren believed serving Barodius would earn his freedom. His mission involved infiltrating the Battle Brawlers, securing the DNA Code, and recruiting powerful brawlers to support Gundalia’s war against Neathia. To this end, he deceived the Battle Brawlers by falsely portraying Neathia as an aggressive invader and supplied them with advanced Phantom Data to develop Bakugan Interspace. Initially self-motivated and dismissive of friendship, Ren nonetheless shared a strong bond with Linehalt. His interactions with the Battle Brawlers were complex; Marucho trusted him, while others like Shun remained wary. After Fabia Sheen exposed his deception, Ren rejoined the Gundalian forces but suffered repeated defeats against the Battle Brawlers. Ren’s loyalty shifted when he witnessed the Twelve Orders’ cruelty, including the punishment of teammates Sid Arkale and Jesse Glenn. Sid’s apparent death and his final gesture of entrusting Rubanoid to Ren proved pivotal. Realizing Barodius had manipulated him and exiled his people, Ren turned against the emperor. He allied with Neathia, became a Castle Knight, and after a symbolic brawl with Fabia Sheen, was fully accepted. After the war, Ren returned to Gundalia and collaborated with Prime Minister Nurzak, whom he respected for past kindness, to establish a democracy. During Mechtanium Surge, he served as Commander of the Gundalian Forces under Nurzak and was a member of Team Grey, fighting against Mag Mel and the Chaos Army in Gundalia. Ren also appears in the online game *Bakugan Dimensions*.