I've been asked by some fans how Mist stays an angel goddess, due to the fact that she's in love with a demon prince and engages in sex acts with him. Well, I have a few answers, mainly my opinions and interpretation on various subjects.
Well, first off, Mist is NOT a Biblical angel. She is a Valkyrie, which is a sort of battle angel from Norse Mythology that deals with rounding up the souls of mortal beings who died recently. The brave and heroic get sent off to Godheim/The Light World, while the weak and feeble get sent to Helheim/The Dark World. Those who won favor in Godheim either become Valkyries (if female) or Einheriar (if male).
To make a long story short, my story takes place in a polytheistic universe, meaning that it's a universe where almost every deity or demon known to humankind exist. It's not so much a black and white morality, as it is a blue and orange morality. It's more Order vs Chaos than Pure Good vs Pure Evil. What is good or evil, or at least acceptable or taboo, varies from region to region of the eight realms of Alerfa. Just like many human cultures of Earth, each civilization, mortal or divine, has their own rules and culture. Not one culture is a like. If all fantasy cultures were black and white morality, it would get kind of boring after a while.
With that being said, why does Mist love Amirani and become intimate with him, despite the fact that she's an angel and he's a devil? Well that's simple. Sex between consenting adults who love each other is not evil nor immoral. I even believe this is true in human culture, despite what soccer moms and focus groups claim. Besides, just because I write about “morally qurstionable” topics in my original universe, does NOT mean I condone them in real life. It's just a fictional science fantasy world, and sometimes, what is written in fiction, should stay in fiction.
Besides, if stories had ratings, a lot (though not all) of my stories would be either R or NC-17. Because I am more comfortable writing for mature audiences than I am for kids and tweens. Feels like I have more freedom of expression when writing for a mature adult audience. No limits and little censorship, just how I like it.
I hope that answers some questions. BTW, world building is time consuming, yet very fun to do and very rewarding at the same time.