I know this sounds strange but why did the first thing that came to mind was INTERLOPER.

I forgot to mention this as well but "Lord of the hammers" and "Dragon blazers" Might also not be accurate to chapter 5 and onwards.

Skyghost and dark Taranza are also very similar (I'll probably explain this in better detail in the future).

Don't worry, it's fine. On the topic of 02, I'm pretty sure it was a reincarnated version of Zero so I don't think it would exist yet if the Zero of Deltarune (ERAM) was still alive.

Like I said in the post, It's probably ERAM aka John Mantle.