He’s just a supremely powerful being (nameless thing, perhaps) who was created at the same time as Arda and who is just content living in a forest singing all day about how hot his wife is instead of caring about anything that happens in the world around him.
The question is, what is his wife, Goldberry? She appears to be a personification of nature, Arda, or just the Old Forest or something.
I saw this coming. If you aim at the king, you best not miss.
I don’t know what made Prigozhin stop his advance, but he must have accepted that he was a dead man the moment he did.