The Crucible Kingdom

In this spin-off of the Blue Moon Rising series, the Crucible Kingdom, an obscure planet far, far away, is suffering from an ancient curse-periodic bouts of violent storms, earthquakes, floods, tsunamis, and wildfire. To break the curse, a widowed duchess and a starship captain from the disintegrating Regulon Empire (which her ancestors fled centuries earlier) are forced to work together. Although the duchess grudgingly accepts that the captain is highly capable in emergencies, she scorns the idea that a hard-headed Reg who does not believe in the power of sorcery can be helpful in breaking a curse.
And then the captain comes up with an idea no one thought of, setting off a quest that turns out to be as dangerous as the curse itself.