But they're worshiped as gods? [ he is more curious than anything ]

I know concretely know of two realms, the demon realm and the human realm. I'm sure there's more out there we haven't figured out how to access yet. They're connected by portals..... In order for the portal to work, though, they need a powerful source, called "titan's blood'.

[ he is kind of excited to talk about this, ngl. he enjoys nerding out ]

I've never been to the human realm, myself, but humans have been in the demon realm before. Portals have been around for at least a few hundred years.