Sorry. My mistake, The Moon uses Tarot cards in Hannah K. Nystrom's Spooktacular comic which is canon.

All of the vampires (except The King) are actually named after Tarot cards and the vampire's use tarot cards. This is probably the input of Jesse Moynihan.

He actually said that he had a three season plan (and he would have revealed the author at the end of season 2 instead of half way through), and now it seems like it is ending this season as he said that it will end when summer ends and Dipper and Mabel leave.