The heart of the eternal

When the leader of a tribe of nomadic elves and humans are told that his fate is to marry a girl from one of the distant inland valleys he is less than thrilled, but the seer has spoken and he isnt one to disobey the Gods.
The girl in question is even less thrilled but when faced with a difficult choice she does chose that which allows her to save her family, it is a small sacrifice after all.
Unbeknownst to them both this will be the start of something which will have far reaching consequences for them all, both spiritually and physically. Can truly a marriage between one of the eternal and a human being function? What about his sworn partner and mate, the one he already does love? And why is it that this seemingly simple village girl has the potential to save them all from an ancient enemy, set on destroying them all?
They say that the power of love can conquer anything, can it truly be enough this time.