I think it would be useful to make the history of TSP world similar to the real world one on a macroscale, especially when it's not really relevant for RP, so up to me dinosaurs existed and were annihilated by an asteroid 65 million years ago.
As far as mythological species, I think they can exist as long as they don't have superpower ( big reptilian winged creature? yes. Flamespitting? No)
Brother Unclepear
Dear Leader of the Voodoo People's Republic of Bruuma
Representing also
El Pollo Diablo
Boss Maximo of the Estado Libre Asociado of Puerto Pollo
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Chairman Lo Pol
Core Leader of the People's Republic of Kai Fa