It always starts with the cosmology, right? Like, you have to make the cosmic rules matter beyond just aesthetics. If their respective heavens and hells are just fancy backdrops, the conflict feels weightless. I'm more interested when the writer uses dogma as a trap. The angel isn't just conflicted about breaking rules; they're terrified that loving a demon might prove their own side's doctrine about corruptibility true. Meanwhile, the demon might be fighting not against their nature, but against a system that defines them solely by it. The real tension blooms in the quiet moments—an angel healing a mortal and feeling a flicker of pride, which is a sin, while the demon watches and feels a foreign ache of... something like reverence. That's where you get the good stuff, when the conflict is internalized as a crisis of identity for both.
Too many fics go for the easy war storyline, armies clashing, but that's just set dressing. The deeper mine is in the philosophical rift. What if the angel's virtue requires forgiveness, but their doctrine says demons are unforgivable? What if the demon's rebellion was justified, and the angel starts to see the cracks in their own paradise's gleaming facade? The plot thickens when their bond forces them to question not each other, but the very foundations of what they are. I read one once where the demon's love literally burned the angel's grace away, not through malice, but because purity couldn't coexist with that kind of touch. Now that's a conflict that hurts.