Illustration of a demon behind bars in a brick wall with red text that is on fire; all on a black background.
In 1979 the then Marriott Great America park redesigned their "Turn of the Century" rollercoasters in both Illinois and California, and rebranded them as the Demon. The storyline explained in the soundtrack is that the park missed payments on the Turn of the Century, and so a demon repossessed the ride. The coaster was painted black and effects such as fog and red waterfalls were added. The theme has remained largely intact since 1979, with a temporary addition of the Looney Toons Tasmanian Devil after the parks' purchase by Six Flags, and some updates to the original Marriott logo.
Marden, Duane. "Demon (Six Flags Great America)". Roller Coaster DataBase. Retrieved from https://rcdb.com/3.htm.