Another way is to make it a result of a potion accident. Harry drinks a wrong potion during Potions class and suddenly gains eagle vision. This could then lead to a series of comical and adventurous situations as he tries to adapt to his new sight.
You could also make it a part of Harry's ancestral magic. Maybe it was an ability that was dormant in his family line for generations, and due to some strong magic around him (like during a battle with Voldemort), it gets awakened. This would tie in with the idea of his special heritage and give a new dimension to his character in the fanfiction. He could use this eagle vision to sense danger before it arrives, similar to how animals with keen vision can sense predators from afar in the wild.
The blurry vision could be a result of a dark magic spell cast by the Dark Phoenix or its followers. This would make it difficult for Harry Potter and his friends to fight back. They would have to find a counter - spell or use their non - visual senses to overcome the obstacle.
In a more detailed plot, Harry's newfound eagle vision might be a side - effect of a powerful spell gone wrong. He initially struggles to control it, seeing things that are too far away or too detailed all at once. As he learns to master it, he realizes it gives him an edge in Quidditch. He can spot the Snitch from an incredibly long distance, making him an even more formidable Seeker. This also draws the attention of the opposing teams who try to find ways to counter his new ability.
You could make it a form of Animagus. A character could transform into a leopard - serpentine hybrid. This would give them unique abilities like the speed of a leopard and the stealth of a snake. They could use these abilities to spy on the Death Eaters or to find hidden magical objects.
One way is to focus on the Gryffindor common room. Have the students in there engage in activities that promote unity, like group discussions about how to face challenges in the wizarding world. They could also plan pranks together against Slytherin, but in a way that shows their unity and loyalty to each other.
You can start by researching different animals and their symbolic meanings. For example, if you want to create a new family in your fanfiction, you can choose an animal like a deer for its grace and swiftness. Then, you can have the family members inherit certain traits related to the deer, like being quick - thinking or having a gentle nature.
Another possibility is that a dark wizard has created a curse specifically designed to create this Jekyll and Hyde - style separation. This curse could target a prominent character like Draco Malfoy. His 'Jekyll' side might still be the proud Slytherin trying to uphold his family's name, but the 'Hyde' side could be a more desperate and power - hungry version, willing to do anything to gain an advantage. This would lead to a complex character arc for Draco and also impact his relationships with other characters like Harry, Hermione, and Ron in new and unexpected ways.
The Death God in Harry Potter fanfiction could be a new, dark force. It may be introduced as an ancient entity that has been dormant for centuries and is now awakened. This entity could be in conflict with the existing magical order in Hogwarts and the wizarding world. It might target certain characters, like Harry, because of his connection to the prophecy and his power to defeat Voldemort. Fanfic writers may use this concept to explore themes of mortality, fate, and the limits of magic that were not fully explored in the original series.
I recall one fanfiction where Draco Malfoy has Eagle Vision. The unique part of the plot is that he uses this ability to try and redeem himself. He sees the true nature of the Dark Mark and realizes the error of his family's ways. With his Eagle Vision, he can detect the approaching danger of the Death Eaters in a different way and tries to warn the other students at Hogwarts, which changes the whole perception of his character.
One way could be to have a character who is a Parselmouth (like Slytherin) discover a hidden green - tinted magical object in the morning. This object could hold the key to a mystery that the character has to solve throughout the day. The green color of the object and the fact that it was found in the morning could be significant, perhaps having a connection to an ancient Slytherin spell or prophecy.
The Master of Death could be a goal in the fanfiction. For example, a group of characters from both universes could be on a quest to either prevent someone from becoming the Master of Death or to help someone worthy achieve that status. Along the way, they would have to deal with the challenges and differences between the two worlds.