Ages of Monsters:
Monster Age Zero: Occurred 85,000-75,000 years ago during the time of Mu. First instance of kaiju being worshipped as Gods. This age ended with the sinking of Mu around the "Toba Super Eruption".
First Age of Monsters:
Occurred from 4000 BC to 476 BC. First appearance of kaiju like Ouroboros, the first known Alpha of the kaiju in its era. Primarily occurred around Ancient Greece, Western Europe, and Eastern Asia. Much folklore has been inspired by this event. First appearance of liminal species derivative of humanity, and first instance of humanity discovering magic and Yggdrasil, the massive tree believed to be the source of magic.
Ended with most mages and liminal species going into the shadows following a decline in magic. Remaining non-nuclear kaiju species enter hibernation.
Second Age of Monsters:
1954-Today. Still ongoing. Most widespread instance of kaiju existing yet. Recent developments include the uncovering of the previous ages. First widespread instance of radioactive kaiju following the atomic era.
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A/N: This will be a very short collection of miscellaneous worldbuilding that was not included in the main story. Work on the sequel is underway.