A German scientist working for the Nazis, and a member of the Thule Society, Dr. Kroenen became one of the top scientists for Project Ragna Rok, and a close disciple of Grigori Rasputin, along with Ilsa Haupstein and Leopold Kurtz. He was present with Rasputin at the secret ritual in Scotland that brought Hellboy to the world.
Kroenen, Haupstein, and Kurtz were frozen inside a secret Nazi base, until they were resuscitated by industrialist Roderick Zinco, acting on Rasputin's orders. Kroenen resumed work on several of his former projects, including making an "Apocalypse Army" by combining corpses with robotics. He also convinced Zinco to retrieve the head of his colleague, Herman von Klempt, from South America. Kroenen retained an affection for his colleague, though Rasputin had rejected von Klempt as unsuitable for Ragna Rok. When von Klempt's head was re-animated, he tried to convince Kroenen to abandon Rasputin's plan - to awaken the Ogdru Jahad - and instead to use the Army to retrieve von Klempt's work in South America. Overhearing, Kurtz became furious and attacked von Klempt's head, screaming, "Rasputin is master!" In a panic, Kroenen seized a knife and killed Kurtz. When their plan failed, an enraged Rasputin struck Zinco blind. Wandering around, Zinco accidentally pressed a self-destruct button in the base, destroying it completely and taking Kroenen with it.
Movie Version Biography
Kroenen was born in Munich, Germany in 1897. As a young boy, he was an opera prodigy. He sang in all of the capitals of Europe until the fatal day when he hit puberty on stage and lost his opera voice and career. He preformed brutal experiments and surgeries on himself due to his addiction. He created his tight-fit gas mask to filter out bacteria because of his vulnerable health from removing his lips and eyelids. In, 1930 he met Grigori Rasputin and soon became loyal follower. In, 1933 he joined Hitler’s SS and soon after joined The Thule Society, a nazi occultism group. He assisted in Project Ragna Rok, where the group conjured the scarlet beast, Hellboy. Their plan was flawed due to the attack from the allied forces. In the attack, a grenade was detonated and blew off Kroenen’s left hand and sent a chunk of shrapnel through his chest. It was after this that he seemingly disappeared. In, 2004 he reappeared and resurrected Grigori Rasputin. He was trapped in a pit where Hellboy dropped a cog over him to trap him after killing his father.
Kroenen has kill allied troops, BPRD agents, and Trevor Bruttenholm, the man who through the grenade which took his hand and appositely his life.
His role in the movie is similar to his role in the comics with a couple of alterations to his body's anatomy and choice of weapons. He is portrayed by Ladislav Beran while his voice is provided by the film's director: Guillermo Del Toro himself.
Hellboy II: The Golden Army
While he didn't appear in the sequel, his damaged mask is seen on display in a glass case at the B.P.R.D. headquarters.