Game designer Sandy Petersen isn't afraid of anything. Well, almost anything. "The revelation that things are not as they seem—that's scary to me," says Petersen, the guest of honor at this weekend's H.P. Lovecraft Film Festival. "Like in [2002 Japanese horror film] Dark Water, when the mother's holding her daughter in the elevator, and then she sees her real daughter coming out of the room. That's terrifying."

For a man credited with designing a good many terrifying games, this is a big admission. Petersen created the 1981 Lovecraft-inspired Call of Cthulhu tabletop role-playing game, now in its sixth iteration. Players, called investigators, face a situation doomed by extraterrestrial or demonic forces, but that's where similarities with other RPGs, like Dungeons & Dragons, end. "The game's not about killing the monsters," says the 57-year-old, who lives in suburban Dallas. "They're stronger than you anyway. You're doing intellectual research."

After his Cthulhu RPG, Petersen went digital. Those scenes in 1993's wildly popular video game Doom, where a rocket launcher stands unguarded in the middle of a massive room that comes alive with demons as soon as the weapon is touched? That was Petersen's design, along with 19 of the game's 27 levels. He contributed as well to games like Quake, Darklands and Civilization. Last year, Petersen attempted to create an iPhone game called Cthulhu World Combat, but the Kickstarter campaign fell short of its goal. Still, gamers celebrate Petersen as skilled at the intellectual side of both history and horror.

The same could be said of Lovecraft himself. Though he mostly wrote for pulp horror magazines like Weird Tales in the '20s and '30s, his writing has a depth completely foreign to most modern horror. As in Petersen's game, Lovecraft's protagonists are scientists without special powers who suddenly see their worlds overrun with the "Great Old Ones," godlike ancient monsters. Many of his stories are framed as letters or essays, replete with obtuse descriptions. In the story "The Call of Cthulhu," Cthulhu is described as "a monster of vaguely anthropoid outline, but with an octopus-like head." No writer has more horrifically beaten around the bush.

Dozens of Lovecraft-inspired board, card and video games have been made over the years, including Call of Cthulhu games for both PC and the iPhone. But Petersen's Call of Cthulhu role-playing game out-nerds even the nerdiest Lovecraft fans. When asked to sit down and play the game, Lovecraft Bar owner Jon Horrid declined. "We're a different kind of nerd than the role players," he said.

Petersen says he doesn't mind. "People who like Lovecraft may or may not pick up the game, and that's fine," he says. "But role players that aren't Lovecraft fans like it because it's a premier horror game."

But given how wistfully Petersen speaks about Lovecraft, it's clear his alliances lie with the Lovecraft camp rather than the RPGers. "Lovecraft doesn't let you go back to the normal world," Petersen says. "You're trapped, and everything you know is wrong."

SEE IT: The H.P. Lovecraft Film Festival runs May 3-5 at the Hollywood Theatre. Weekend passes $60, day passes $15-$25. For schedule, see