If Harry Potter creates a virus in fanfiction, it could be a virus that was initially meant for a good purpose. For example, it was supposed to target dark wizards only. But something goes wrong, and it starts to affect everyone. He then has to use his knowledge of potions and magic that he learned over the years at Hogwarts. He might also have to seek help from the professors who have more in - depth knowledge of complex magic. Harry would be on a race against time to find a cure before the virus spreads uncontrollably.
In a fanfiction where Harry Potter creates a virus, perhaps it's a virus that affects magic itself. The virus could spread through spells and start to corrupt the very essence of magic. Harry, realizing the severity, might then have to team up with his old friends like Hermione and Ron. They would search for ancient magic or rare potions to counteract the virus before it destroys the entire magical ecosystem.
The plot could start with Harry finding an ancient Jedi artifact during one of his adventures. This leads him to become curious about lightsabers. He then uses his magic knowledge to try and replicate it. Along the way, he might face opposition from some in the wizarding world who think it's too dangerous or against wizarding traditions. But Harry, being the hero he is, persists. Eventually, he creates a lightsaber and uses it to defeat a new, powerful dark wizard who has emerged, using both his wizarding skills and his new lightsaber skills.
In a 'Harry Potter creates a shelter' fanfiction, perhaps Harry uses his magic to create a shelter in the Forbidden Forest. He might use spells like Protego Totalum to make it safe from dark creatures. It could be a place where he hides his friends during a dangerous time at Hogwarts, like when Voldemort's forces are on the prowl.
One possible plot could be that Harry, after defeating Voldemort, decides to create a kingdom where magic and non - magic folk can live together in harmony. He uses his knowledge of magic and the respect he has gained to build a new society with its own set of laws and governance that are fair to all. For example, he could create schools that teach both magic and Muggle subjects to promote understanding between the two worlds.
Well, perhaps Harry Potter, using his magic, accidentally creates the world of Remnant from RWBY. He might then have to deal with the new and strange creatures and powers there, while also trying to find a way to get back to his own world.
One possibility is that Harry Potter, using his knowledge of magic and experiences, decides to create a school for mutants. He could use spells to protect the school from the outside world and those who might fear the mutants. He might also teach the mutants how to control their powers, just as he learned to control his magic at Hogwarts.
The reaction would be complex. Some wizards would still have faith in Harry and believe that he can fix the situation. They would support him in his search for a cure. However, a large part of the wizarding world would be very suspicious. The Daily Prophet would be full of stories about Harry, some of which would be full of false rumors. The Hogwarts students would be divided, with some believing in their former classmate and others fearing him.
Well, it could be about Harry using his skills and magic knowledge to custom - create a super - powered Firebolt. Maybe he adds some unique enchantments to it for speed or stealth.
Well, it could be a wild mix of magic and mutation. Maybe Harry Potter uses his magic to accidentally create a mutant in the world of 'sch' (whatever that is in the fanfiction context). It could lead to a whole new set of adventures as he tries to deal with the consequences of this creation, like trying to find a way to control or help the mutant.
It could be a planet where magic is more powerful and less restricted. Harry, having faced so many limitations in the wizarding world he knew, would create a place where magic can be used freely for good. There could be no dark wizards or threats like Voldemort, and wizards could focus on exploring and expanding their magical abilities. For example, they could create new spells without the fear of them being used for evil.
If Harry were to create a Horcrux in fanfiction, it would likely lead to a great corruption of his soul. Horcruxes are dark magic, and the act goes against all that Harry stands for in the original series. He might start to show signs of increased aggression, a detachment from his friends, and a growing attraction to the Dark Arts.