Trick or Treat Exchange

They're separate canonicals now, but they didn't use to be. (There was also a Hellenistic Religion and Lore canonical for a little while, but AO3 seems to have dropped that even though they've still left it as the disambiguation in some of the current canonical character tags. The ways of AO3 are mysterious.) I think that a combined Greek and Roman Mythology works fine and is the simplest, but I can work with either.