For Raven, her dark magic could be weakened. Maybe she tries to use her powers to levitate a glass of water to her bedside but fails. Her connection to the otherworldly forces that fuel her magic is disrupted by the sickness in her physical body.
Beast Boy's power might be affected in that he could have trouble shifting shapes. When sick, his body may not be able to handle the energy required for complex transformations. For example, he tries to turn into an elephant but can only manage a small mouse form.
Raven's introverted nature and Beast Boy's extroverted nature often lead to comical and heartwarming moments in fanfiction. Beast Boy might drag Raven into social situations she would normally avoid, like a team party. Raven might be annoyed at first but then realize she enjoys it. Their personalities also interact in a way that helps them deal with emotional issues. When Beast Boy is feeling down, Raven can offer her calm and understanding, and when Raven is struggling with her inner demons, Beast Boy can provide some much - needed levity.
Their powers could interact in a complementary way. Naruto's demon powers might give him enhanced strength and speed. Raven's powers, which are often associated with magic or some kind of psychic ability, could be used to control or direct Naruto's more chaotic demon powers. For example, she could use her powers to calm Naruto when his demon side is about to go out of control.
Storm's power over the weather could be enhanced by Beast Boy's animal forms. For example, if Beast Boy turns into an eagle and flies into a storm cloud that Storm has created, he could disrupt the electrical charges in a way that Storm can then manipulate to create a more powerful lightning strike.
Storm's weather - controlling powers and Beast Boy's shape - shifting could interact in a combat scenario. For example, Beast Boy could shift into a large bird and fly into a storm cloud created by Storm to gain an aerial advantage against an enemy.
A third plotline might be that their sickness is caused by some sort of magical or alien virus. As they fight off the illness, they also have to figure out where it came from and how to stop it from spreading to the rest of the city. This could involve some detective work even in their weakened state.
Their powers could interact in really cool ways. Zatanna's magic could be used to enhance Beast Boy's shape - shifting. For instance, she could use a spell to make his animal forms stronger or faster. In return, Beast Boy could use his animal senses when they're on a mission together. If Zatanna is trying to find a hidden magical item, Beast Boy in his animal form could sniff it out or sense it in a way that Zatanna's magic alone might not be able to do.
One possible analysis is that it explores a unique relationship between two characters. Fanfics often delve into the emotional and romantic aspects that might not be fully explored in the original source. It could show how their different personalities, Raven's more reserved nature and Beast Boy's more exuberant one, interact and create a compelling love story.
One possible fanfic could be about Beast Boy and Raven getting stuck together while decorating the Titans' tower for Christmas. Maybe Beast Boy accidentally turns into a reindeer and Raven has to use her powers to control him. It could be a really funny and heartwarming story of their friendship during the Christmas season.
A 'beast boy x raven lonely beast fanfic' could be full of emotional depth. Since Raven often has a complex and somewhat withdrawn nature, and Beast Boy is more outgoing. In this fic, their dynamic might be about Beast Boy bringing out a different side of Raven. It could also involve some kind of adventure or situation where they have to rely on each other, especially when Raven is in her 'lonely beast' form which might come with its own set of powers and challenges.
His friends might be in awe of him at first. They would see him as even more powerful and might rely on him more during battles. For example, if he has new powers like controlling the elements, they could use his abilities to their advantage in strategic ways.