Which is the biggest red flag, Veeky Forums?
>The GM's game setting is bog-standard medieval high-fantasy set in a faux Europe with woodland elves, orc hordes, wizard towers, and dwarf mines. Effectively indistinguishable from Dragonlance or Forgotten Realms, save a bunch of new proper nouns to learn and some new geography to put on the map.
>The GM has set out to avoid "generic fantasy" as hard as possible, resulting in every imaginable convention being arbitrarily turned on its head. The setting has elves and dwarves, but THESE Elves all pilot magitek mechs, and THESE dwarves all live in floating airships. Setting may or may not have another genre layered on top of high fantasy, like "Post Apocalyptic" or "Gaslamp Fantasy," even though the party will still spend half their time going dungeon delving at the end of the day.
>The GM's setting is "self-aware." He's set out to deconstruct all the "tropes" he can, often with some comment about "what if the implications of X in a fantasy setting were taken to their logical conclusion." Civilized races are all definitely assholes, but the monsters are probably misunderstood and he'll make you feel bad if you kill them.
>The GM's game is set in a "dark fantasy" world. The peasants are all dying of plague, the nobility is all greedy and inbred, the elves are bloodthirsty cannibals, and the magic is not-so secretly powered by "spoopy" Lovecraftian cthulhu monsters. Gods are either distant or dead. Your paladins will definitely be dead too in a few sessions.
>The GM's setting is 'WACKY!' He probably calls it "gonzo fantasy." The gnomes ride two-headed cats and the wizards all grow mushrooms in their beards that give them magic and someone will probably make a Monty Python joke every session, because it's SUPPOSED to be silly, man!