For future visitors, to help clarify what is meant by "myriad gods" (八百万の神) in the Demon Marbas commentary, Shinto beliefs has three main variations of
Kami:
- Amatsukami (天津神) - roughly "the gods of the heavenly realm", refers to Kami who reside in the sacred fields of heaven Takamagahara, plus those who were born there and later descended to Japan. Amaterasu, Tsukuyomi, etc. are included under this category
- Kunitsukami (国津神) - roughly "the gods of the earthly realm", they are often tutelary deities of the land. Susanoo-no-Mikoto, Okuninushi, etc. are included under this category
- Yaoyorozu-no-Kami (八百万の神) - roughly "the countless Kami", this is a more general classification that can be equated to Animism, of divine forces of nature residing in everything deserving of respect like mountains, waterfalls, boulders, animals, trees, thunder, ghosts, etc.
(Worth noting, 八百万/8 million was an expression of countlessness at the time)
Kondo-sensei's comments from point number 3 onwards specifically referred to the 八百万の神/Yaoyorozu-no-Kami as the spirit participants of the turf war against Demon Marbas, prior to the final sealing at Kyoto by the Buddhist Nisho Temple.
Meaning no superpowers like the Amatsukami, the Kunitsukami or or other foreign gods (like Hariti) were present, just the local glorious Nippon neighbourhood spirits and their human shaman buddies chasing foreign invaders out of their homes for a millennia. One can only wonder how things would turn out if superpowers DID participate...
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Incidentally, this struggle happened in the 1000 years between the Yayoi Period (1000 BC to 300 AD) and the Nara Period (710 AD to 794 AD) - in other words, before Abe no Seimei was officially born in 921 AD during the Heian Period.
Also, you can't quite tell from this translation, but in this comment, Kondo-sensei was very insistent on the phrasing of " [悪魔マルバス]と呼ばれていたモノ ", or "the thing that is referred to as [Demon Marbas]". This long winded phrasing is used three times, plus once near the start as " [悪魔マルバス]と呼ばれていた霊的なモノ ", or "the spiritual thing that is referred to as [Demon Marbas]"
In other words, by continuously using "thing" (モノ), he's emphasising that this entity is not the full Marbas itself, but a thing resulting from an insufficient summon, yet is nevertheless addressed as Marbas for convenience's sake by its summoners.