Arceus has been summoned. You have been working tirelessly. Reading old scripts, uncovering tales on how to summon the God. Finally, at the spear pillar in Sinnoh, you have summoned him!

"Greetings young one, why is it that you have summoned my presence?"

He speaks with telepathy, his 'voice' has a sickening judgement and regal tone. He would not waste the resources to send his true form, the Arceus present is merely a vessel he uses to interact with his lesser creations.