The Kanji used is different from the usual 助, but the meaning and nuances remain unchanged. As for the magic context, since magic is something that empowers you to do many things that would be impossible, including more directly saving/assisting/helping people, animals, and objects, becomes possible. More context would be ideal, but the idea in this text is probably about the choice of saving/assisting/helping something, while keeping something away, and that doing so be both a blessing and a curse, a medicine and a poison, and so on.

Depending on the full context, it's also a good idea to keep in mind another meaning that 援ける can have, which is 見逃す, in the sense of 見咎めずに済ますこと。But with the amount of context I have at the moment, "What to assist/help/save" is more likely to be the most fitting translation.

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Note added at 3 hrs (2023-02-12 21:22:06 GMT)
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To build a little more on the first premise. The idea is also about choices. The choice to save or assist certain things, while keeping other things away and how such choices can become either a blessing or a curse, or it can become both, like you suggested, of course. But I think the key concept here is potential. It has the potential to become helpful just as much as it has the potential to become harmful, and it even has the potential to become both at the same time. Since the source text appears to be rather ambiguous, it may be a good idea to keep some of that ambiguity in your translation as well, but try to look at the full context, as it may help make your translation more clear and natural, while keeping it accurate.