I mean, he is your character, so his backstory is yours to make. I just gave an idea.

but he’s a Head-Hunter, right?
also, he had the ability to create metal weapons and stuff.

Died? If you go by that logic, then that means sekiro and metal gear have already died.
I’m just saying that people can still like what they want and make content of it if that’s what they wish, it doesn’t really matter if it’s an old thing. People still make parodies and stuff of invader zim, so why not undertale?

Because it’s a good game that people like.