Okay I came up with a better and marginally less derivative monster idea, if this is still accepting them.
It's a radioactive dragon.
Now I know you're going to say "hey that's just Godzilla" but bear with me. I meant this thing is an active radiological monstrosity in a way that Godzilla is never really presented. Radiation seethes off of this thing in invisible toxic waves, and its heart is a burning nuclear reactor, like a stellar core. Also more emphasis on the Dragon part, as it fully resembles a winged dragon.
I think this thing is going to be an alien of some kind; a stellar parasite that lives on the surfaces of stars and feeds on their fusion-bodies.Here's the sample art.