Though it is true that Girantia is supposed to be the creators antagonist, which is in all world religons
Um... no. Such a figure appears in a few modern religions, but overall, very few religions over the course of history have had a supreme evil figure. Sure, most have had some form of evil beings involved, but not very many had a Satan-figure. Since most modern portrayals of older myths have been under Christian influence, it has become common practice for modern storytellers to portray one of their gods as Satan. Let's use Greek mythology as an example. In many modern retellings, Hades is shown as being evil. In the original source material, Hades was a cold, uncaring figure, but really wasn't actively plotting wickedness (the kidnapping of Persephone wasn't very nice, but it still isn't enough to justify Hades' demonization). And, as anyone with a decent knowledge of ancient Greek belief can attest, even the 'good' gods were selfish, callous, and jerks in general. Modern storytellers tend to be uncomfortable around the idea of having the gods' morality not being portrayed in black-and-white terms, and thus change the status quo around a bit.