Say we did do the "Elf Medicine for Shallyans" action (which is still only a vague possibility rather than a certainty, given it comes with the pricetag of a whole KAU purchase and 2APs worth of CF). And say we end up with a Minor/Moderate Shallyan Boon, rather than a polite thank you (it is a donation rather than an exchange, after all). How would we want to spend such a thing?
Off the top of my head, theres:
- Rights to Shallyan libraries for KAU. Kinda a prosaic use for a rare boon, but "We gave you books, you give us books" is pretty symmetrical.
- A Shallyan miracle worker to try out Windherding with a non-Teclisian tradition. Nothing really stands out in the Wiki's list of noted Shallyan miracles as a "wow" combo with any of the other winds we have access to, but the point would more be the act of Windherding itself rather than whatever the product would be.
- The Cult of Shallya joins the Waystone Project. A Divine Magic perspective from a major Cult is definitely one aspect we're missing. It's possible there could be insights there on tributaries or leylines. Shallyan endorsement might also open some doors for getting rollout accepted, given their popularity among the laity. But then they're pretty non-political (which is part of why they remain so popular), so an endorsement isn't a given.
- Stockpiling it to pull a Heidi later on to get the clock turned back. I don't think one boon would be enough, Mathilde has other paths to longevity available to her, and old age is very unlikely to be the thing that does her in in the end. So I'm not hot on this one.
I guess my vote would be for Windherding cooperation? Unless we need something political from the Cult that I'm not thinking of.