🎃 Hallowe'en Treasure Hunt 2023; hints for 12

Jack-o-lantern 12

What rocks they are, but every year.
Copley Lawn is filled with fear.
A film on film, the scene its own,
By budding bulldogs keenly known:
Chapel, graveyard, stacks beware,
And stumble not the fatal stair! (Tim)

8 Petroglyph: #12: The riddle contains the location Copley Lawn, which is in Georgetown, Washington DC. Nearby is a set of stairs (also mentioned in the clue) that feature prominently in one of the most famous horror movies of all time.

( 40 Tanya-dogearedcopy: And I was overthinking #12 (anti-hint: It's nothing to do with the words "Hoya Saxa" or the gargoyle drain spouts)
Figures they would be a "Tim clues"! 🎃)

52 anglemark: The movie is cataloged here (basically all films are). It's a true classic and was released fifty years ago.

54 perennialreader: The movie starred Linda Blair. Was a much-talked movie at the time.