The Baskils could potentially be a family related to some existing characters in the Harry Potter universe. Maybe they are distant cousins of the Weasleys or have some connection to Hogwarts in the past. They could have been a family that was once powerful but lost their status and are now trying to regain it with Harry's help. Or they could be a family that has always been in the shadows and Harry's friendship brings them into the spotlight. In the fanfiction, they could have unique appearances, like having a distinct hair color or eye color that is characteristic of their family.
Well, it could be that the friendship leads to some interesting cultural exchanges within the wizarding world. The Baskils might introduce Harry to some of their family traditions which are different from what he's used to in the wizarding world. For example, they could have a unique way of celebrating magical holidays. And Harry, in turn, could share his Gryffindor experiences and values with the Baskils. Maybe they end up collaborating to solve a mystery in the wizarding world that no one else could figure out because of their combined knowledge and skills.
It could be Nagini. Even though in the original series she was more of a servant to Voldemort, in the fanfiction, she could have a different personality and form a bond with Harry.
Harry Potter's best friends are Ron Weasley and Hermione Granger.
The Weasley twins could also be potential allies. They are always up for some mischief but also have a good heart. They could use their creativity and knowledge of Hogwarts' secrets to help the fem Harry Potter in her journey as the heir. For example, they could help her find hidden areas of the school where she might learn more about her heritage.
He could become friends with Jimmy Olsen. Jimmy is always curious and open - minded, so he would be likely to be interested in Harry's magical world. Harry could show Jimmy some simple magic tricks, and they could bond over their shared sense of adventure.
Hermione Granger is often a popular character in such fanfictions. Since she is a Muggle - born witch, she has a unique connection to the Muggle world. Writers might explore her relationship with her Muggle friends before she went to Hogwarts or how she still keeps in touch with them during her time at school. She can act as a bridge between the two worlds in the stories.
Hermione could be a main character. She might be the one who first notices the strange changes in Harry after he becomes friends with Death. She could try to research about this unusual friendship in the library, using her vast knowledge to understand the implications. Ron could also be important. He might be initially skeptical about Harry's new 'friend' but then come to accept it as he sees the positive effects it has on Harry and the help it provides in their fight against dark forces.
He might turn to his studies more intensively. Since he has no friends to distract him, he could pour all his energy into learning new spells and magic, becoming more powerful in the process.
It could be that he is wrongly perceived as dangerous. After all, he has survived the Killing Curse as a baby and Voldemort is always after him. People might be afraid to get close to him for fear of getting caught up in the dark wizard's wrath.
The Ministry of Magic could also be the main antagonist in this case. If the Ministry is corrupted or under the influence of dark forces, they could manipulate Harry's friends. They might convince his friends that Harry is a danger to the wizarding world order, and his friends, being naive or misinformed, end up betraying him.