In Astarion BG3 fanfic, some of the popular themes include his redemption arc. Given his past as a vampire spawn who has done some not - so - nice things, many fanfics explore his path towards redemption. His relationship with other party members in the game is also a popular theme. For example, how he interacts with Gale or Shadowheart. And of course, his internal conflict. The constant battle between his dark desires as a vampire and his new - found sense of morality.
One popular theme is Astarion's struggle with his vampiric nature. Many fanfics explore how he copes with his bloodlust and the moral implications. Another theme is his relationship with the main character. Whether it's a romantic or a platonic bond, writers like to delve into the dynamics between them. Also, his backstory often gets explored, like his time as a slave to Cazador and how that has shaped him into the character we see in the game.
Well, in Astarion BG3 fanfic, a common theme is his journey of self - discovery. Since he has been through so much trauma, fanfiction often focuses on him finding his true self. Romance is also a big theme. Fans love to write about his relationships, especially the more tender and loving sides of him that might not be as obvious in the game. And then there's the theme of power. How he gains or loses power, and how it affects his personality and relationships.