They can add drama. For example, if a character suddenly discovers they are a 'Lord', it can create a power struggle within the story. Others may be jealous or try to use the newly titled character for their own gain.
Well, in Harry Potter fanfic, titles like 'Baron' or 'Baroness' can be quite interesting. These titles can often be associated with certain areas of the wizarding world or particular families. They might come with specific rights and responsibilities. For instance, a Baron could be in charge of a certain magical estate or be responsible for the magical protection of a region. It gives fanfic writers a chance to expand on the social and political structure of the wizarding world.
Titles of nobility can create power struggles. For instance, if a young prince wants to claim the throne but an older duke with more influence opposes him, it can lead to a major plot point.
Monsters can be a major plot device in Harry Potter fanfic. They can change the relationships between characters. For example, if a monster attacks a group of students, it can make them bond together more tightly as they fight for survival. Or, if a character has a special connection to a monster, like being able to communicate with it, this can lead to a whole new sub - plot. The monster might hold a key to a mystery, like the location of a powerful magical object, and the characters' quest to get that information from the monster becomes a central part of the plot.
Familiars in fanfic can affect the plot in many ways. For instance, they can be used as a means of communication. If a wizard is in a dangerous situation and can't use magic openly, their familiar can carry messages to other wizards. They can also act as a plot device to introduce new magical elements. Say a familiar discovers a hidden magical artifact, that then becomes the focus of the story.
They can drive the plot forward. If a character takes an oath to find a powerful magical artifact, then the whole story can revolve around that quest. It gives a clear goal and motivation.
The 'angel of music' in Harry Potter fanfic can affect the plot in multiple ways. If it is a benevolent entity, it may guide the protagonists to discover new spells or magical artifacts. For example, it might lead them to a hidden chamber in Hogwarts where a powerful musical - themed magical item is stored. On the other hand, if it is malevolent, it could create chaos by causing students to lose control of their magic when they hear its music. This would then lead to the characters having to find a way to either stop the 'angel of music' or protect themselves and the school from its influence.
They can introduce conflict. For example, if the 'creature of the night' is a powerful vampire clan that decides to take over Hogwarts, the main characters will have to find a way to defend the school. This creates a lot of action and suspense in the plot.
It can greatly change the plot. If Harry has a different name, like Ethan, for example, Voldemort might not target him as easily. This could delay the start of the main conflict in the story. Or, it could cause the Order of Phoenix to be more cautious in approaching him as they may not be sure if he's the 'Chosen One' with this new identity.
It can drive the plot by creating a strong bond between the characters. For instance, if they are facing a powerful dark force, this unity can be the key to their survival and victory. It might lead to new strategies and alliances being formed.
When Harry has the power of teleportation in fanfic, the whole concept of travel and rescue missions is transformed. He can instantly transport himself and others out of dangerous situations. This power can also lead to new adventures as he can explore far - off places without the need for traditional means of transportation, thus opening up new storylines.