Karlheinz is the main antagonist of the otome series Diabolik Lovers where he acts as the one who influences a lot of the events indirectly, usually using secret identities and political movements to get his aim across. He is the father of 11 confirmed sons, 6 biological ones.

• His aim in the project "Apple of Eve" is to get killed by either Adam so he could transfer him the power to rebuild the world.
• The Vampire King can foresee the events to unfold in future.
• He is both a doctor, politician and a king for 2 worlds. (Vampire Clan and Demon World)
• "Karlheinz" means free man and rules of the household
• He calls Socrates his "dear friend" in the game constantly. Despite the otherworldly tricky situation, he has candid debates often over a chess game. It is specified, by Karlheinz's words that he won at least 183 times.
• Elberth, the Wolves King, and Karlheinz have a close relationship, often visiting each other. During the war between Giessbach and Karlheinz, he refused to ally with the Founder King.
• Contrary to the belief he is immortal, it has been proven he can die by getting his heart stabbed with a silver knife.
• He can shapeshift and change his appearance at will. That includes becoming either a man or a woman.
• He doesn't like getting his hands dirty.