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Lucifer's a way nicer guy than God there. And ignoring that, can you really say Giratina is Pokesatan? Oh sure, it looks devilish, but the six legs/ribs/streamers is coincidence(like how people thought President Reagen's name proves he is the Antichrist), we aren't given information for why it is "the renegade" and it's job suggests it has an actual position/is an actual deity instead of a fallen spirit. The Torn World is creepy and weird, but it isn't Hell. Really, the closest "mythological" figure would be the old ones of H.P.Lovecraft(like them, Giratina is alien, from another dimension, atypical of our opinion of gods, and hard to understand). The "Giratina is Satan" is just a fan theory, like "Blue's Raticate", and there's nothing to confirm that any Judeo-Christian elements were added to Giratina(or Arceus for that matter, though it pretty much is a creator god. Just not the one we're familiar with)
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I disagree, Giratina is really closer to Shinto God Tsukuyomi and the Distortion World certainly has elements of Yomi. But it also does have elements comperable to Lucifer, much like Arceus is a collective amalgamation of creator deities including YHWH(I mean, for crying out loud the Plates are pretty much inspired by classical depictions of Moses' Ten Commandments, there is literally church devoted to Arceus in Hearthome City, and you literally encounter him on top of a Stairway to Heaven) while being closest to Izanami and Amenominakanushi, Giratina seems to be a composite of rebel gods and entities, including Lucifer, but also deities such as Mot of Ugratic pantheon.
(also comparing him to Yog-Sothoth is kinda BS considering Yog-Sothoth is supposed a personification of time and a bunch of floating balls, and Giratina is most certainly neither).