A sense of duty to his angelic brethren. Even though he has become friends with the Winchesters, he still has a connection to the angels. If the angels convince him that the Winchesters are a threat to the celestial order, he may betray them to uphold what he believes is his true duty to heaven.
Love can be a motive. He might fall in love with someone who has different goals from the main characters. If this person convinces him that the Winchesters' actions are wrong, he could betray them. For example, if he falls for an enemy of the Winchesters who has a more 'peaceful' approach on the surface, he may be swayed.
Perhaps in the fanfiction, Castiel betrays the group because of a misunderstanding. There could be a miscommunication regarding a prophecy or a powerful artifact. He might think that Sam or Dean are going to misuse it and decides to take it for himself to prevent that, but in reality, they had no such intention. This creates a rift between them and is seen as a betrayal.
One possible motive could be a lack of emotional connection. Maybe the wife felt that despite her husband seeming perfect on the surface, they didn't truly understand each other on a deeper level. Another reason might be a mid - life crisis. She could be feeling unfulfilled in her life and made a bad decision as a result.
Jealousy could be a major motive. Maybe someone is jealous of their talents, like their combat skills or their ability to make friends easily. For example, a less - skilled ninja might feel overshadowed and decide to betray them to get ahead.
Power could also be a factor. Suppose there's a powerful object or ability that only one of them can have. Travis may be tempted to betray Percy to get it for himself. He might think that with this power, he'll be more respected in the camp.
Dumbledore might be motivated by his over - arching plan to defeat Voldemort. He could see Hermione as a sacrifice that needs to be made. Maybe he believes that by betraying her, he can gain some crucial information from the enemy that will ultimately lead to Voldemort's downfall.
It could be that Peter has some sort of knowledge or information that the kidnappers want. For example, he might have accidentally witnessed a crime and the criminals want to keep him silent.
Perhaps Castiel is left behind in a dimension where time moves differently. He watches as years pass by in the blink of an eye outside of his prison - like dimension. He can see the world changing, but he's unable to be a part of it. His longing for his friends and his purpose with them grows with each passing moment, and he starts to question if he'll ever be reunited with them.
The fanfiction might show Meg dealing with the physical and emotional changes of pregnancy while still being her tough self. She might have to fight off those who would try to harm her because of the baby. Castiel, on the other hand, would be by her side, using his powers when necessary. It could be a story of their growth as individuals and as a couple.
In Supernatural fanfiction, Castiel's mind is significant because it's a window into his character development. His mind changes as he forms bonds with Dean and Sam. His thoughts about loyalty, sacrifice, and love are all shaped by his experiences. His mind also holds the key to understanding his unique perspective on the war between angels and demons. For example, he might think about different strategies to end the war that are influenced by his angelic knowledge and new - found human emotions.
Castiel's mind in Supernatural fanfiction is a fascinating topic. His experiences, such as being resurrected multiple times and his interactions with other supernatural beings, shape his mental state. In some fanfictions, his mind is explored through his dreams or hallucinations. These could be manifestations of his subconscious fears and desires. For instance, his fear of losing his friends might appear as a menacing figure in his dreams, representing the threats that constantly surround them in their supernatural adventures.