It is weird to me that Shinigami is considered "an existence that defies reason" in this fantasy world...
I always treat that kind of translation as "too literal"/"TL/PR showing incompetence in actual english".
Along the lines of "This is not our/you don't have "common sense", which is just as cringe-worthy.
From the image and context, I feel the proper translation would be:
"It's a Myth come true/alive."
Alternatively: "So the legend is true..", although that one might trigger the Literalists..
Same as Shinigami wouldn't be "a type of god", but rather "(divine) spirit".
But to be fair, translating japanese concepts of spirituality into english, with its
completely different concepts is a pain-and-a-half.
I quite often feel a translation would be better off simply using the direct romanisation in these cases, given that you're dealing here with a (set of) concept(s) that really have no equivalent in modern english, and are more of a complete ..
Gestalt with its own cultural flavour and associations.
Not unlike keeping the japanese suffixes in names, since they don't have much meaning in english, but are
very important indicators for relationships in the story.