Perhaps it's about power. If he can turn Buffy, a powerful slayer, into a vampire, he could gain more influence in the vampire world. He might think that having a slayer - turned - vampire by his side would make him more feared and respected among other vampires. Also, he could use her newfound vampire abilities for his own evil deeds. He may also be motivated by a twisted sense of love or possession. Since he has a complex relationship with Buffy, he might want to keep her with him forever in the vampire state.
In fanfiction, Angelus could be motivated by the desire to break the natural order. Buffy represents the force that maintains the balance between good and evil as a slayer. By turning her into a vampire, he would be disrupting that balance in a very extreme way. He might also be doing it just for the sheer fun of corrupting someone so pure - hearted. It gives him a sense of satisfaction to see Buffy, who stands for all that is good, fall into the darkness of vampirism.
One possible motive could be revenge. If Buffy has previously defeated him or his plans, he might want to turn her into a vampire as a form of ultimate revenge, to make her into the very thing she has been fighting against.
Well, Angelus is a very cunning vampire. He might manipulate Buffy's emotions. For example, he could make her believe that becoming a vampire is the only way to save someone she loves. By preying on her heroic nature, he tricks her into a situation where she is vulnerable to being turned into a vampire. He may also use false promises or misinformation about the so - called 'benefits' of being a vampire in the fanfiction world.
One possible plotline could be Buffy's friends rallying together to rescue her. They might use their unique skills, like Willow's magic, to track down Angelus and his lair.
Another motive could be related to a plot for a school event or performance. Maybe the organizers of a school play or a skit need a boy to play a girl's role for comical effect or to add an interesting twist to the story. They might trick the boy into agreeing to it without fully disclosing the details at first.
Love and sacrifice also play a big role. There could be a situation where Angelus has to make difficult choices to protect Buffy and the unborn child, or Buffy might have to sacrifice her slayer duties to some extent for the sake of the pregnancy. These themes of love, protection, and sacrifice are often central in such fanfictions.
Common themes include the duality of their natures. Buffy is a hero, and Angelus is a villain, yet they are drawn to each other. The theme of secrecy also pops up often. Their relationship can't be out in the open easily. Lust is a very obvious theme considering the 'lemon' nature of the fanfiction. But there are also themes of sacrifice, where either Buffy or Angelus might have to sacrifice something for the other or for the greater good in the context of their relationship.
Popular themes often include redemption arcs. If Angelus were human, how would he seek redemption for all the wrong he did as a vampire? Also, love and friendship are big themes. Fans like to write about how Buffy and Angelus could have a more 'normal' love story as humans, or how their friendship could develop in a different way. There are also themes related to the challenges they face in a human world, like dealing with mortality, which is very different from their vampire - filled existence.
The allure of 'angelus is buffy mate fanfiction' lies in the complex nature of their relationship. They are two very different characters, one a slayer and the other a vampire, which creates a lot of tension.
Jealousy could be one motive. Maybe Katherine is jealous of Elena's popularity and relationships, so she turns her into a vampire to make her life as difficult as hers. Another motive could be power. By turning Elena, Katherine might be trying to gain some sort of control over her or use her for her own plans.
One common theme is the struggle between good and evil, especially with Angel and Angelus. Since Angel has this dark side in him, a lot of fanfics explore how he tries to keep Angelus at bay while also being with Buffy. Another theme is love and sacrifice. Buffy often has to sacrifice her own feelings for the greater good when it comes to Angel and Angelus.
I really liked 'The Three - Way Dance'. In this fanfic, there's a lot of action and emotional turmoil. Riley's insecurities about Buffy's past with Angelus are brought to the forefront. And Angelus, with his dark allure, adds an extra layer of tension. The story takes you on a roller - coaster ride of emotions as you see these characters deal with love, jealousy, and their own destinies.