Well, to awnser your question.
Arceus is God, Giratina protects Palkia/Dialga from Harm, but if they were to battle, Giratina finds them as a threat. Giratina is also a reverse of Arceus, which show he is the ruler of death and chaos.Giratina is Satan, and the Distortion World is A Mystic like Hell, Were Giratina is more offensive if anything that is not dead, so It's like an intruder.
so I just said that Giratina would play the role as the Devil in the pokemon world