meaning - What does the following sentence say about field fires?

My friend and I are reading the book 宝石泥棒 by Masaki Yamada.

The first scene is in a Jungle, and the protagonist, a young warrior in primitive attire, is just about to continue on his journey when suddenly there is a strange flash of blue light, a wave of heat hits the young man, and a fierce fire starts.

The following text follows. It seems to be meant to describe how fierce the fire is:

少年は色を失っていた。いかに勇敢な戦士といえども、押し寄せる炎に抗することはできない。

炎は、死神の使わしめ、〝髑髏の猟犬{カーマン}〟に譬{たと}えられている。確実に、そしてすばやく、その犠牲{ぎぜい}者たちを牙{きば}にかけるからである。野火がどれほど恐怖の対象となっているかの、一つの証左といえた。

What we don't understand exactly is this last sentence: 野火がどれほど恐怖の対象となっているかの、一つの証左といえた。It seems to say "It could be said to be a proof of the degree to which field fires become the subject of fear". But something must be missing in this translation. What is the proof of what?

What does this sentence say about field fires and the fire that just occurred in the story?

Edit:

Since the source of the confusion may be the way we interpret the beginning of the text, here is my translation of the first sentences:

The boy paled. A brave warrior though he was, he could not stand up to the advancing flame.

Now, the 炎 in the next sentence could be "flames in general" or "these particular flames that are advancing on the boy", so the translation could be either:

Flames are likened to the messenger of Death, "The Hound of Skulls".

or

These flames were like the messenger of Death, "The Hound of Skulls".

And next:

This is because they would sink their fangs into their victims without fail and very quickly.

(Note: the author seems to expect us to be familiar with the expression "髑髏の猟犬", even going as far as giving it a non-standard furigana. I couldn't find any relevant references, though).

My expectation as a reader is that this whole passage would explain why a brave warrior should fear the sudden flames so much. In the paragraph that follows this text, the boy starts running away as fast as he can. Either it's something frightening about fires in general, or something frightening about this particular sudden unnatural fire. But that last sentence doesn't seem to be about that. And being in the past tense seems to imply that it should be an observation relevant to the scene and not a general observation about field flames.