Herman von Klempt is a Nazi 'mad scientist' who has worked on numerous schemes to control or destroy the world. Though his body was destroyed, von Klempt survived as a head in a jar, often assisted in his work by his mechanical apes.
A German scientist, von Klempt was a close colleague of Karl Ruprecht Kroenen at university and it was Kroenen that saved von Klempt after the explosion that lost him his body. Although the two men apparently shared similar ideas, von Klempt was not recruited by Grigori Rasputin as a disciple, preferring scientific work over occultism. Von Klempt was assigned to other Nazi projects.
In 1939 von Klempt was made head of a Nazi space program based in Hunte castle, that attempted to recruit extraterrestrials into the Nazi regime. The operation however was stopped by American troops and the rocket crashed into the hanger doors, killing all in the facility, save von Klempt.
After the collapse of the Nazi regiem von Klempt tried to destroy America with a plague of vampires by sending a rocket filled with the undead to the states. Once again the operation flailed in an explosion caused by the BPRD’s founding member professor Broom. The torsoless Nazi was next sighted in Brazil were he attempted to make armies from super soldiers (created by dead convicts) and early Kriegaffe. He was however defeated by Hellboy (Broom's adopted son) and the BPRD on several occasions over the 1950s.
At some point in the mid 90s von Klempt's dormant head was delivered to a revived Kroenen, at a Nazi facility in Norway, by a Roderick Zinco. However, after restoring von Klempt the two argued over Kroenen's allegiance to Rasputin resulting in Rasputin's ghost blinding Zinco, who then stumbled on to a button that destroyed the entire facility.
Von Klempt once again resurfaced at Hunte castle, the site of his original space program. Here, with the help of his granddaughter, he called signalled the shuttle he sent in 1939 to land at the castle; proving that his space program was in fact successful. Despite the efforts of Hellboy and the BPRD the shuttle landed, transforming into a huge worm-like creature that devoured all in its path. Eventually a particular BPRD agent by the name of Roger, managed to destroy the worm by flowing a large electrical current through it. During the events Roger also flew von Kelmpt's head at a mountain side, apparently killing him.
Von Klemmt's mummified head spent some time in the offices of Zinco cooperation (the industry owned by the Roderick Zinco mentioned above) and was last seen in the hands of his old colleague Karl Kroenen, as he exited a ruined Manhattan.