I am arguing against the idea that the crystals are an opportunity that we'll be able to replicate from another source. Other than being directly told secrets by the gods, I don't see how else Mathilde will be able to learn anything about how they do what they do.
I think I understand where my confusion comes from.
I fully agree with you that the crystals present by far the best opportunity for researching what gods are literally made of. If that was your point, my confusion was in expecting something which I disagree with.
The meaningful sacrifice bit was more related to being contextual / emotional belonging.
I think it would be appropriate for Mathilde not to do experiments with Ranald's stuff without consent. (Tacit acceptance has been given so far, what with him overlooking her experiments and only objecting to one single experiment so far… and that one it turns out would have been dangerous to Mathilde's mental health.)
I don't think it is appropriate for Mathilde to hand over the decision on whether she will continue research on
other divinities (including using the crystals) to Ranald. If he seriously objects, I'd still stop, but that is just a general thing. If Ranald seriously asks Mathilde to stop
anything I'd most likely vote for stopping that.
The divine energy itself isn't of any use if we want to understand what the gods actually do with that energy. The crystals won't be useful because they contain divine energy, but because they contain divine energy that has been captured in a very specific pattern that we can actually take the time to look at and interpret.
I'm pretty sure any divine energy would work. "what gods actually
do with that energy" is simply "subsuming it into being
their own energy", which every divine energy they have inherently does.