Well, perhaps it could be about Harry being injured in a battle and coughing up blood. Maybe he's in a fight with a dark wizard and gets seriously hurt.
In this fanfiction, it could be that Harry is exposed to some dark magic that affects his lungs. He starts coughing blood and this is the start of a long journey for him to recover. His friends Hermione and Ron would then be on a quest to find a cure for him. They might search through old magic books in Hogwarts library or seek the help of some wise magical creatures.
It could be Voldemort. He might have cast a new spell on Harry that makes him cough blood as part of his ongoing attempts to defeat Harry.
One idea could be that the blood test is a school project at Hogwarts. Students are required to do a detailed analysis of their own blood magic. Hermione would be super - excited and dig deep into research. Harry might be a bit worried as his blood has some unique connections to Voldemort. Ron, on the other hand, could discover something unexpected about his Weasley bloodline that has been lost in history.
In Harry Potter fanfiction, a blood donor could be a very interesting concept. Maybe a character needs a special blood type to recover from a dark curse. For example, if a student was poisoned by a rare magical plant, and the antidote required the blood of someone with a particular magical lineage. A brave Gryffindor might step up as a blood donor, showing the selfless nature that the house is known for. This could also create a lot of drama and tension in the story, as the act of donating blood in the wizarding world might have unforeseen consequences, like an unexpected magical bond forming between the donor and the recipient.
It might be a story where a wizard or witch is a huge Shiba fan and during a routine blood test in the Hogwarts hospital wing, they discover that their love for Shibas is somehow encoded in their blood. This could lead to all sorts of adventures, like finding a secret Shiba - filled magical realm accessible only to those with this 'Shiba - in - the - blood' trait.
One possible plot could be that Harry discovers an ancient spell or prophecy that requires him to bathe in dragon blood to gain the power to defeat an even greater evil than Voldemort. So he embarks on a dangerous quest to find a dragon and obtain its blood.
It could involve Harry Potter taking a stand against a dark wizarding family that has wronged his loved ones. Maybe they've targeted his friends or family, and he decides that a blood feud is the only way to deal with their ongoing threats and attacks.
Blood in Harry Potter fanfiction can act as a plot device in multiple ways. It might be used to create mystery. Say, a strange symbol appears when a character bleeds, and it's related to an old prophecy. It could also be a factor in alliances. Characters with similar blood - related powers might form an alliance. And in some fanfictions, the discovery of a character's true blood heritage can completely change the direction of the plot. For instance, a character thought to be a Muggle - born might turn out to be from an ancient and powerful pure - blood family, which then throws the whole story into a new light with new opportunities and challenges for the character.
The plot could start with a mysterious portal opening between the two worlds. A Hogwarts student might accidentally stumble through it into the world of Strike the Blood. This would lead to a series of adventures as they try to find their way back home. Along the way, they could meet the characters from Strike the Blood and learn about their world. The student could also introduce some basic magic concepts to them. As news of this strange visitor spreads, it could attract the attention of both the good and bad forces in the Strike the Blood world, creating a lot of tension and action.
Yes, it can be considered popular among certain groups. The idea of a 'blood god' in the context of Harry Potter fanfiction allows for a lot of creative freedom. Writers can explore new magical concepts, dark magic, and unique character developments. It might not be known to the general Harry Potter fan, but those who dig deeper into the fanfiction realm often come across such interesting and niche genres.
I'm not sure of a specific one, but a unique plot could be where the acid blood is a key to unlocking a hidden power within Hogwarts. The character has to figure out how to use it without harming themselves or others.