Something I'm selling. A heaven, earth, and hell AU. Note those who are born demons can be reformed.
Adrien a destructive black cat demon is the son of the demon Gabriel/Hawkmoth and his human wife Estelle. He is disgusted by demons for being half human and feared by humans for being half demon. The only person who cares for him is his mother, his father loves him as well but keeps his distance from him because he fears his Hawkmoth persona will force him to hurt his son. As a teenager he is befriended by the guardian angel ladybug who's kindness causes him to fall in love with her. Though she loves him too she rejects him because she's immortal and doesn't want him to be hurt. Though she longs to become human so she can marry him and have a family. One day someone kills her, in grief Adrien uses his demonic powers to accidentally paralyze the part of the earth where he lives.
Fifteen years later Marinette discovers the frozen land and undoes the spell. When Adrien sees Marinette he thinks she's Ladybug because she looks exactly like her but learns from the priest master Fu, that before Ladybug died she prayed to become human so she could be with Adrien. God pityited her so he granted her wish by having her be reborn as Marinette a human girl. However Marinette has no memory of ever being Ladybug. Adrien at first has no interest in Marinette because instead of being the confident and strong ladybug she's a shy little girl. But what Adrien doesn't understand is that this is who Ladybug always dreamed of being.
Shortly after this a darkness called Akuma is released into the world and it influences people into becoming demonic like creatures. Marinette despite being human still has Ladybug's angelic powers of healing and creating. So she and Adrien team up to cleanse the akumatized humans. Joining them is Fu's apprentice Nino, an amazon warrior called Alya, Tikki Marinette's cat who she is surprised to learn is a holy pet and Plagg Adrien's demonic cat.
Other characters include Chloe a baron's daughter who is destined to marry a feline demon and believes that to be Adrien. Nathaniel a lion demon who has a crush on Marinette. Felix Adrien's half brother who Gabriel fathered with the jinn Natalie. Bridgette Fu's granddaughter who Felix is reluctantly assigned to protect along Wayzz a jinn turtle. Kim, Alix, and Max three trickster Imps. Ivan a gentle bear demon, Mylene an angel (a forbidden love between those two). Lila a halfbreed fox demon like Adrien, she lusted for him but he loved Ladybug so she killed Ladybug out of jealousy though Marinette does have a fearful instinct around her, and Theo a wolf demon who lusted after Ladybug and tries to marry Marinette thinking she's Ladybug due to the resemblance
maybe I'll write this if no one bites.