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.
One of the main themes is the alteration of their destinies. In the original story, their fates are tied to the vampire - slayer - vampire world. But in human fanfiction, writers often explore how their destinies could be different. Another theme is family. How would their family relationships be if they were human? For instance, would Angelus have a different relationship with his family members? And of course, there's the theme of self - discovery. As humans, they would have to rediscover who they are without their vampire or slayer identities.
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.
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.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). It has a vast collection of Buffy - related fanfics, including those about Buffy and Angelus in a human context. Fanfiction.net is also a popular option, but the quality may vary more. Another place could be Tumblr, where some fans might share their own fanfiction or recommend good ones.
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.
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.
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.
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.
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.
One of the popular themes is the exploration of their relationship in a more ordinary, human context. Without the supernatural elements, their love - hate dynamic can be reimagined as a complex human relationship. For example, they might be two people from different social circles who are drawn to each other despite their differences. Another theme could be their personal growth. Buffy could be dealing with normal life challenges like career choices and family issues, while Spike might be struggling with his own past traumas and trying to become a better person. And a third theme could be the power of friendship within their group. They could be part of a diverse group of friends, and their relationship with each other affects the whole group dynamic.
A must - read Buffy Angel Angelus fanfic is 'Soul Searching'. It explores the concept of the soul and how it differentiates Angel from Angelus in a very profound way. The author does an excellent job of bringing out the emotions of the characters. Also, 'Darkness Rising' is a good one. It starts with Angelus being unleashed and follows Buffy's journey to stop him, with lots of action and some great character development along the way.