
He didn't. His concubines were given as the society was building around him. He has never visited any of them, but since they are technically his consorts as well, they are treated with similar care to Nain. Even Gwen lol!
Amon doesn't really care and listens (a bit too much) to his Grand Priest who constantly gives out suggestions.

Amon has never interacted with the Leshas. He does not have any other consorts besides Nain. The Leshas, if I remember correctly, were actually appointed for Nain's sake. It's revealed in the novel that Nain used to love going to Lotus Hall (where the Leshas reside) and interact with them. However, after a certain incident, Nain decides to avoid Lotus Hall and interacting with the Leshas altogether to protect their lives saftey.
Amon never had any interest in the Leshas. This hasn't been explicitly stated in the novel I don't think, but based on his character, I don't think he's ever step foot in Lotus Hall. He's also, most certainly, never had affairs with the other Leshas. Amon views every human being besides Nain as nothing more than an insect.
just caught up with the novel. i think there are still a few more side stories left so i haven't finished it yet, but essentially there is no true endgame i guess you could say. nain ends up living with both amon and gwen in trastasa. amon and gwen absolutely despise each other, but they recognize that if they kill each other, nain will kill himself (he will no longer have the will to live). so they've come to a mutual agreement to maintain peace with each other for nain's sake.
in terms of trastasa itself, the country changes drastically by the end. human sacrifices are banned altogether. people are kind to each other. there is no blatant corruption among the priests. everything has changed to better suit nain's best interests. nain, himself, is much, much happier as a whole.
from my understanding of it - nain both loves and hates amon (it's complicated lol) and loves gwen. he also loves trastasa and all the people he came to love in the past, despite the painful memories he harbors.