Well, a common concept could be that the Leviathan is a threat in the fanfiction world. Harry, as an Animagus, might have to use his unique abilities to protect others from the Leviathan. His Animagus form could give him an advantage in speed or stealth. Maybe he can fly closer to the Leviathan in the form of a bird Animagus to study it without being detected. Or if he's a cat - like Animagus, he could use his agility to escape from the Leviathan's attacks while trying to figure out a way to defeat it.
One interesting concept could be Harry Potter's Animagus form interacting with the Leviathan. Maybe his Animagus form is a small creature like a mouse, and it has to find a way to communicate or avoid the Leviathan. Another idea is that the Leviathan has some sort of magical connection to Harry's Animagus ability, like it can sense when he is in that form. Also, perhaps Harry uses his Animagus form to explore a hidden world where the Leviathan resides, and discovers secrets about the wizarding world that were previously unknown.
Perhaps a Basilisk Animagus could have a special connection with the other snakes in the wizarding world. In the story, they could communicate with snakes to gather information. This would give them an edge in situations like uncovering plots within Slytherin house, as the snake is the symbol of Slytherin. They might be able to understand the secrets that the snakes around the Slytherin common room are aware of.
One interesting concept could be characters having multiple animagus forms. For example, a character might be able to transform into a bird and a cat. This could add new layers to the story, like how they use different forms for different tasks or to solve mysteries.
In non - sexual Harry Potter fanfiction, Animagus could be used in various ways. For example, an Animagus character might use their form to spy on Death Eaters. They could transform into small animals like a mouse to sneak into hidden places where important information is stored. Another concept could be using the Animagus form for self - discovery. A character might learn more about their true nature by experiencing life as an animal.
His Animagus ability might be enhanced. The danger posed by the Leviathan could make Harry more in - tune with his magical side. For example, if his Animagus form is a stag, he might become faster or more powerful in the presence of the Leviathan. It could also be that the Leviathan has a certain magical aura that affects Harry's transformation. Maybe it makes it easier or more difficult depending on the situation.
One interesting aspect could be seeing Harry's new form as an Animagus. Maybe he turns into a unique animal that gives him different abilities and perspectives in the wizarding world.
One interesting plotline could be Harry discovering his animagus form earlier than in the original series and using it to secretly explore Hogwarts at night. He might find hidden passages or secrets that were previously unknown.
One interesting Animagus Harry Potter fanfic could be one where Harry discovers he's an Animagus earlier in his Hogwarts years. For example, he might transform into a stag like his father, and this new ability helps him in various adventures, like sneaking around Hogwarts unnoticed to uncover secrets. Another could be a fanfic where Hermione is an Animagus, perhaps a cat, which would add an interesting dynamic to her character as she could use her feline form to explore hidden corners of the library or spy on the Slytherins.
Some fanfictions in Harry Potter 2 might play with the idea of the basilisk having different powers or weaknesses. It could also explore the idea of a hidden connection between Ginny and the Chamber of Secrets that goes beyond what was in the original story. There might be fanfictions that change the role of certain characters, like making Neville a more central figure in solving the mystery of the Chamber.
One interesting fanfiction could be where a character discovers they are a bird Animagus in a completely unexpected way. For example, they might be in a dangerous situation and suddenly transform into a bird to escape. This adds an element of surprise and adventure to the story.
One interesting 'Harry Potter' fanfiction about Sabertooth Animagus could be where a character discovers they have this unique ability. Maybe they use it to protect Hogwarts in a time of great danger. For example, they could be spying on Death Eaters in their Sabertooth form without being detected.