The theme of lost purpose can be seen as well. Castiel's purpose in life can get muddled, especially when he starts to question his angelic orders. This confusion and the feeling of being adrift in a world that he doesn't fully understand lead to his sadness. These themes are often intertwined in 'castiel sad fanfic' to create a rich and complex emotional landscape for the character.
Betrayal is also a theme. Sometimes he is betrayed by those he trusts, which causes great sadness. For example, when his fellow angels turn against him. And there's the theme of unrequited love. His feelings for certain characters may not be reciprocated, adding to his sorrow. This is often explored in 'castiel sad fanfic' to show the depth of his emotional turmoil.
The theme of unrequited love can be common. Maybe Castiel has feelings for someone who doesn't return them. Guilt is also a big one. He might feel guilty for actions he took that had negative consequences. And the idea of being an outcast. Since he's different from both angels and humans in many ways, he often feels like an outcast, which brings about a lot of sadness in fanfictions about him.
One common theme is Castiel's struggle with his angelic nature. He often has to balance his loyalty to heaven and his newfound connections with humans.
Another theme is self - loathing. In 'castiel depressed fanfic', he frequently blames himself for things that have happened, whether it's his actions in battles or his perceived failures in protecting others. This self - loathing is a big part of his depressive state.
The theme of self - discovery is also prevalent. As a female Castiel, she has to figure out her place in the world, both as an angel and as a female entity. This often involves her coming to terms with her new identity, learning about her powers in a different context, and finding her role in the fight against evil in a more female - centric way.
Reflection is also a big theme. Castiel has a long history, and on his birthday, he may look back on all the things he has been through, the people he has met, and the choices he has made. This can add a lot of depth to the fanfic and make readers understand his character better.
The theme of sacrifice also pops up a lot. Castiel may have to sacrifice his angelic duties or powers for his wife, or the wife might sacrifice her own safety or desires for Castiel. This creates a sense of drama and emotional depth in the stories. For instance, in one fanfic, the wife gives up her chance at a normal life to stay with Castiel in the dangerous world of angels and demons.
There can be a theme of spiritual discovery as well. In some fanfics, his blindness is seen as a way to connect more deeply with the spiritual realm. It can be a way to show that there are other ways to 'see' beyond physical sight, and it adds a really interesting layer to his character.
A common theme is the power struggle. Castiel is often seen as a more 'pure' angel, while Lucifer is the rebellious one. Their interactions are filled with this underlying battle for dominance or influence. Another theme is redemption. Sometimes Lucifer is portrayed as having a chance at redemption, with Castiel being a key factor in that.
The theme of protection is often present. Castiel, being an angel, has a natural inclination to protect. So in these fanfics, he not only babysits but also safeguards the children from various threats, whether they be physical or more supernatural in nature. For example, in some fics, he might protect the kids from demons while trying to make them eat their vegetables at the same time.
One common theme is the struggle between good and evil. Castiel is an angel, and Meg is a demon, so there's always that conflict. Another theme is redemption. Meg might be seen as someone who could be redeemed through her relationship with Castiel. And of course, love is a major theme. Their relationship, which is so unexpected, often leads to stories of love conquering differences.