Crystalline dragons with prismatic breath require gems for hiring - checkmate!

Yes, that's because green dragons require them, but Kirins might be associated with crystals because they are connected to celestial Water, and after the rain, a rainbow appears, and their heads resemble the heads of green and gold dragons from Heroes 3, where they required crystals. Which resource would you prefer to assign to them?

By the way, would it be appropriate to rename the "Elven Luck" ability for Nags to "Luck of the Sea Elves" instead of just Nags?