Hannibal King was born in Milwaukee, Wisconsin. A private detective who made a modest living, King was bitten and killed by the vampire Deacon Frost while on a case in London, England. Waking up to find himself one of the undead, King was horrified at what he had become and vowed never to consummate the curse by passing it to another. Thus, King would subsist on blood that he purchased (or stole) from blood banks and fed on corpses or animals. King also preferred not to use his vampiric powers, believing that he gave up a part of himself every time he did so. In spite of his vampirism, King continued to operate as a private detective, but could only travel freely at night.
In Blade Trinity, however, it was stated by Hannibal King that he was changed into a vampire by his mistress Danica Talos, stating that he dated her after a brief meeting with her and then became her "Vampire Cabana-boy". He in other words became her vampire slave until the Nightstalkers finally rescued him and injected him with a vaccine which cured him of his vampirism, he then became one of the Nightstalkers to battle the forces of vampire society and Drake.
As a vampire, he first battled Dracula, the Lord of Earth's vampires. While searching for Deacon Frost, King eventually met Blade, the vampire hunter. It was also Deacon Frost who killed Blade's mother. Initially distrustful of each other, they nevertheless teamed up to destroy Frost. King battled a Blade doppelganger created by Deacon Frost. King and Blade then destroyed Deacon Frost himself. King and Blade parted as eternal friends.
At the time of these stories it was revealed that King had been a vampire for about five years. While investigating the murder of a friend at the hands of the Darkholders, King contacted Doctor Strange, the Sorcerer Supreme. Through Strange, King discovered that the Darkhold contained the spell not only for creating vampires but destroying them. And it was through King that Strange learned of the apparent return of Dracula. King, with vampire hunters Blade and Frank Drake, joined Strange in their visit to Castle Mordo where they retrieved the Darkhold. They battled Dracula and the Darkholders, and then used the book to cast the Montesi formula. This spell destroyed Dracula and all current vampires on Earth and prevented any more from being able to exist on Earth. King was not destroyed by the Montesi formula because he had never taken blood from a living human being, but still required Doctor Strange to perform a complete blood transfusion for King to survive, which restored him to human form.