Gen Con. Indianapolis. Every year, tens of thousands of gamers flood the city with their dice and costumes and yes, even their gamer funk. As it happens—thanks to overlap with myriad other fringe and taboo interests—it is also one of the largest concentrations of occult believers the United States sees all year.

And in 2019, this year, Gen Con is attacked by supernatural beings. Hysteria grips the convention as attendees go from merrily rolling dice to trying to escape with their lives. Who would do this? Why would they do this? And most importantly: Who’s going to stop them?