Hellboy was introduced in 1993 at the San Diego Comic-Con by Dark Horse Comics for distribution at the fan convention. Created by writer-artist Mike Mignola, the stories have a flavor of supernatural adventure with a dark mood embodied by Mignola's line-work, and his distinctive balance of heavy shadows and colors. Hellboy's adventures begin in the 1940s and last into the present day, and involve investigations into the paranormal, including sorcery, Nazi occultism, the Thule Society, hollow earth explorers, werewolves, vampires, and ghosts. Of particular note is the recurring machinations of the Ogdru Jahad, malevolent deities akin to Lovecraft's Old Gods, and the key to their release, the Right Hand of Doom, a relic adorning Hellboy's arm.