Wind Follower by Carole McDonnell

A fourth tribe has come to the land of the three tribes; the light-skinned newcomers are fated to change the tribes' way of life and religion. Satha, a dark-skinned woman from a poor Theseni clan, and Loic, her wealthy young Doreni husband, are too busy forging their new life together to pay much heed. But when Satha is dishonored and Loic must avenge her, they find themselves drawn into a cultural battle. Kidnapped and enslaved, Satha strives to retain her autonomy. Loic struggles against the Arkhai, spirits who fear his his quest will lead him to the true god whose place they have usurped. With the Creator's aid there remains hope they will be reunited and find their mutual destiny, even if it means losing the love and respect of their comrades, families, clans, and tribes.