Why is the 「ようとして」 construct used here?

Question

I was playing The Legend of Zelda, the Ocarina of Time, and the great deku tree says 「今{いま}、ハイラルはその力{ちから}に飲{の}み込{こ}まれようとしておる。。。」, which as far as I can tell means "Right now, Hyrule is being swallowed up by this power." It seems, however, to be worded as though it meant "Right now, Hyrule is trying to be swallowed up by this power" because it uses 「ようとして」, which I've been told means that somebody is trying to do the verb in question.

Who is trying to do what in this scenario/why is it worded this way?

Answer 1

It's definition ⑦ in 大辞林, under 助動詞「よう」:

⑦ （「ようとする」の形で）それが実現する直前であることを表す。 「家を出ようとするところに，電話がかかってきた」 「助成金がうち切られようとしている」

The key word here is 直前. In your example, その力に飲み込まれる is something that's about to happen.

This meaning of 〜(よ)うとする is distinct from the volitional meaning you describe. How do you know which one works? Well, I hope it's clear that その力に飲み込まれる expresses a non-volitional situation, so the volitional meaning isn't compatible with it. On the other hand, this "about to do/about to happen" meaning is compatible with non-volitional situations, so it makes sense here.

You can find the same meaning under 助動詞「う」, of course:

⑥ （「うとする」の形で）それが実現する直前であることを表す。 「叫ぼうとして目が覚めた」 「まさに沈もうとする夕日」

It's the same ending, but う and よう are categorized as separate auxiliaries in Japanese school grammar and in monolingual dictionaries.

Answer 2

It is a stylistic way of saying that something is about to happen.

Hyrule is not yet swallowed up, nor is it being swallowed up, but it is in a state where it is about to be swallowed up.

Essentially, it is "on the brink" of entering the new state which is described.