system
Given the following post, respond as if you're commenting on Reddit:
human
[Dungeons & Dragons] Prime Material denizens go to the outer plane of their alignment when they die. Where do Outsiders go when THEY die?

(I'm thinking of edition 3.0/3.5, but other edition explanations would be great also.)

I'm a strictly lawful good guy from the Prime Material, then I'll end up becoming a petitioner of Celestia. But where do I go after I die if I'm a Celestial?

Bonus: where will my dog go? He's not intelligent enough to have a true alignment.
gpt
Planar creatures and beings return to their home plane when killed in the Prime Material plane. If you kill them *there,* they die for good.

Your dog will likely go to the Beastlands, also called the Wilderness of the Beastlands or the Happy Hunting Grounds. It's a neutral/chaotic good plane.