The Insurgent and Renegade Pokemon

Arceus, the Insurgent Pokemon.
At the beginning of time, it defeated Giratina to become the ruler of the universe.
Giratina, the Renegade Pokemon.
An extremely ancient Pokemon- it was defeated by Arceus and banished to another dimension. It seeks rulership once more.
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In the Torren region, there was a great war. What war, you might ask? The war between two extremely powerful legendaries. Giratina, the God of Pokemon, fought a vicious battle with the Insurgent Pokemon, Arceus. After a long time, Arceus narrowly managed to defeat Giratina. Arceus then banished Giratina to the Distortion World in order to become the ruler of the world. Arceus also rewrote history, making everyone believe that it was the true god of them all. But what if none of this ever happened? Alan Ranger, a trainer from the present world, learned the truth about Arceus and travelled back in time with the help of a Pokemon to stop Arceus and give Giratina back its rightful place as the God of Pokemon.

Inspired from Pokemon Insurgence(with an alternate storyline and universe from the original game)
Amazing cover by @ImberLapis