Kory Bing! — Monster Falls! A continuation (???) of the Mystery...
Gravity Falls | Top 10 Monsters | Oh My Disney - YouTube
Is this monster 8 Ball? : r/gravityfalls
Monsters/Demons/Creatures – Gravity Falls About
Creatures of Weirdmageddon | Gravity Falls Wiki | Fandom
10x4 collage of qwertyprophecy's "Monsters and Mysteries" series of posters for every episode (source and alternate layout in comments) : r/gravityfalls