I'm not sure specifically as I haven't read it. But generally, it might be about various bargains people make and the subsequent betrayals that occur within the context of the story in the '13 to life' world.
One of the best betrayals in fiction is in 'Macbeth'. Lady Macbeth betrays her own moral code and manipulates Macbeth into murdering King Duncan. This act sets off a chain of tragic events that ultimately leads to their downfall.
In 'The Godfather', Carlo Rizzi betrays Sonny Corleone. Carlo, who was married to Sonny's sister Connie, sets Sonny up to be killed in a trap. He does this out of jealousy and resentment towards the Corleone family. Also, in 'Macbeth' by Shakespeare, Lady Macbeth betrays her own moral code. She encourages Macbeth to murder King Duncan so that he can become king, which leads to a downward spiral of guilt and more bloodshed. Then there's the betrayal of Edmond Dantès in 'The Count of Monte Cristo' by Fernand Mondego. Fernand, who was once Dantès' friend, helps send him to prison out of envy and to win Dantès' fiancée.
I'm not certain as I haven't read it. But it could potentially be about the complex relationships between characters which might lead to betrayals, and perhaps there's some element of the supernatural or strange happenings related to the 'strange angels' part.
One common theme is loyalty. In 'mafia bargains twilight fanfiction', both the mafia members and the Twilight characters have their own groups they are loyal to. For example, the Cullens are loyal to each other, and in the mafia, there are family - like loyalty structures. Also, danger is a prevalent theme. The danger that comes from the mafia's violent nature and the vampires' thirst for blood creates a tense atmosphere throughout the stories. And of course, there's the theme of forbidden love. Just like in Twilight, but now with the added complication of the mafia world, making the relationships even more complex and dangerous.
Judas Iscariot from the Bible stories (which are also a form of religious fiction in a sense) is very well - known for his betrayal. He betrays Jesus for thirty pieces of silver, which leads to Jesus' crucifixion.
There are indeed. In some fanfictions, the bargains with merpeople can be quite complex. It could involve trading magical knowledge or a rare spell in exchange for help from the merpeople. This can lead to exciting adventures and new relationships between the human and merpeople characters in the fan - created stories.
Brutus from 'Julius Caesar' is a very notorious betrayer. He was so close to Caesar, seen as a friend, yet he took part in the assassination plot. His actions were driven by his belief that Caesar was becoming too powerful, but his betrayal was still a huge shock. Then there's Iago from 'Othello'. Iago manipulates Othello into believing his wife Desdemona is unfaithful, all out of his own jealousy and spite, which ultimately leads to tragic consequences.