20,000 years ago. An ancient advanced civilization arose in power, its inhabitants mastering what would become magic by the events of Hilda and by using it became so advance due to using earth's aether (What it'll be called instead of mana since the word is from Polynesian culture) as its power source. It was advanced for its time and powerful flourishing for 8,000 years, but unfortunately by 12,000 years, massive sea serpents (Based on Jormungandr) thirst for that power and constantly attacked the great civilization. Despite their strength, the best they could is fend them off at most, wanting to permanently rid of the threat of their great civilization. They had created the Gyaos who soon destroyed the great serpents that had continued to threaten them.
Though successful, it was soon apparent they had made a mistake, the Gyaos, creatures that lacked aether being nothing but artificial creations soon became ravenous turning on their creators. Desperate, they soon created the Gamera's, only this time using their spiritual power of humanity. By this time though, it was too late for the great civilization as they knew it was no more, the Gyaos' soon reached the mainland devouring everything living, prompting guardians the Mountain Giants to interfere. It was here that the Gamera's also soon arrived where they immediately sparked an alliance with the Mountain Giants leading to a great war against the Gyaos, the Shadow of Evil and Embodiment of Death.
It was long but in the end, the Mountain Giants and the Gamera's triumphed but not without massive casualties. Most of the Mountain Giants had died in battle and only one Gamera was the only survivor of his species. The surviving mountain giants expressed extreme sorrow and sadness towards the surviving Gamera being the last of his kind. Both holding each other in high regard. The surviving Gamera would then return to the ruins of the once-great civilization that created him and his kin which was slowly starting to slowly sink due to the damage wrought to it. The surviving Mountain Giants would continue living their lives but since that very day,
Less than a few dozen survivors of the civilization soon eventually left going to the mainland to start new lives, all but one who decided to stay behind due to being the linkbond wielder of Gamera and knowing he was coming back and wanted to ensure for if the Gyaos were to ever return, the linkbond of the previous wielder could be passed onto its next person that Gamera would make contact with just as he returned going into deep hibernation as the civilization continued to slowly sink beneath the waves until it could no longer be viewed. there was a reason before most had departed, one giant would sit atop the tallest mountain, which was a long-forgotten peak in the north at all times. On top, they would just sit and stare, being on "watch duty" for anything that might attack the Earth from up above. They were watching in case the Gyaos would ever return. When the surviving giants were forced out of their world by humans (Except for Jorgen and Illus at the time) they knew that Gamera would still be there if the Shadow of Evil emerged once more.
The surviving members of the once-great civilization would then pass on their knowledge and experience regarding their magic passing it on to those which would eventually lead to the origin of witches, marras as well as trolls learning to master it but in their own way differing from witch magic. (edited)
The stories of the once great-civilization and the ancient war were sparse, rarely speak upon for the horrors humans, trolls, elves, vittras, nisses, and other species had to endure when the Shadow of Evil had first appeared that they had wanted to forget it had all happened. Barely talked about, the stories vanished eventually becoming nothing more then believed to be that of legend and myth.
It was hoped Gyaos, the Shadow of Evil was truly gone but during the ancient war of the Gamera's and Mountain Giants against them, some Gyaos' had apparently laid eggs in very remote areas barely explored or ever touched upon. Two adventurous humans came upon some of those eggs that laid dormant for 12,000 years hatching upon sensing prey. This hatching eventually leading to others around the world to hatch leading way to the events of Hilda and The Last Hope, Gamera.