In regard to the earlier discussion about how many terrestrial avatars are out there, I believe Tenzen mentions that they are "five powerful gods" (not just "powerful gods") created by the mothercrystals to protect Vana'diel, so that's where people get the whole "5 terrestrials only" idea, I think. (5 crystals:5 avatars) However, Tenzen isn't supposed to be all-knowing or anything. It's also worth noting that Diabolos says that he became a terrestial avatar in the "best ending" (if you defeated Promathia) for Waking Dreams, (which might mean that the Vahzl mothercrystal chose him or something) and I think it's also said somewhere that he was "born" in Pso'Xja.
I guess I just assumed that it was after since Shiva looks Elvaan, but that's just aesthetics I suppose. As to how the beastmen originated, I think "beastman/beastmen" is just a term for humanoid creatures that aren't the five races, Zilart/Kuluu, undead, or plantoids (yet stuff like moogles, ahriman, imps, and pixies are excluded). We know that the Kindred, Lamiae/Merrows, and Poroggos weren't created by the Meltdown, yet they are considered beastmen. As such, it is possible that other humanoid animals existed in the time of the Zilart.Actually, they wouldn't be less than 10k years old if those legends took place either before the Zilart came to power or while they were around.
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