>>58555844
They aren't literal corpses, though.
Another thing people keep forgetting when they look at the Primordial Giants in any capacity, even beyond Regignosis, is that Arceus and the Primordial Giants are of the same cloth; Arceus was the lifeform within the egg, and the Giants are the egg that nurtured and protected it until it was ready to hatch. All of them were created simultaneously when the Egg was first wrought into being. Parts of the same whole.
In other words, they're all effectively the same being, they just chose to split up and fight each other for funsies when it was time for Arceus to hatch, because it seemed like an entertaining idea rather than leaping straight into creation without an immediate grand design.
And that battle between Arceus and the Giants was SUCH a fun time that it became a defining attribute of the world Arceus would go on to create, and alongside its own "Normal Type" aspects, Arceus used the aspects from its other selves, the Giants, and imbued them into the world and its lifeforms, which also involved creating the Plates as pure embodiments of those types and a means for Arceus to directly tap into the aspects of its other selves whenever it wants to play by the rules of its own creation.