Ren Krawler is a Darkus Brawler from Gundalia and is also the last descendant of the Protectors of the Dark Bakugan. He originally worked for Barodius thinking he could get his freedom. Later, he was exposed by Fabia, but later returns to the Battle Brawlers and became a Castle Knight. He went back home to Gundalia after the Neathian-Gundalian War ended. As of the events during Bakugan: Mechtanium Surge, he is currently the Commander of the Gundalian Forces under the commands of Prime Minister Nurzak.