Afohdha, the Lady of the Well (2018)

From publisher blurb:

The well’s aquifer runs for miles underground, spanning rivers and cisterns to bring life to the land. Generations of farmers coaxed the water above ground, and rice and grains that grow nowhere else in the East paid for gilded thrones. Three principalities once waged war over Afondha’s Well, dark blood seeping through earth to mingle with the water. Now they have reached an equilibrium through treaties and marriage, so each may prosper.

Afondha is a regional fertility goddess. She has scores of god-blooded children, begotten with men and women from all three princedoms, whom she views as extensions of herself. They fill her retinue as guards, servants, spies, and — for those born of prestigious mortal lineages — ambassadors. She has no patience for rebellion or laziness, and swiftly disowns any children who refuse to play their parts. Any who actively betray her, or even speak badly about her in public, can look forward to unfriendly visits from hireling slavers, assassins, or in some cases their own siblings.