The name of the Dungeons & Dragons club that the Hawkins kids join has not one, but two meanings. First, it's a reference to the X-Men comics, where a group known as the "Hellfire Club" played a significant role in several storylines (including the famed "Dark Phoenix" storyline, which El's recent plot has mirrored to a degree). It's also a reference to the "satanic panic" of the era. Eddie even reads the club a magazine article decrying the "dangers" of letting kids play games like D&D.
As a bonus, Dustin later claims to have hacked a police database with the help of "Cerebro" — aka Professor X's psychic-power device.