Perhaps in this fanfiction, a group of rogue wizards steal Harry as a baby. They plan to use Harry's fame and power to start a new regime in the wizarding world. They keep Harry hidden and try to brainwash him into believing their radical ideas. However, Harry has an inner strength that resists their attempts, and he eventually finds a way to escape and seek the truth about his real family.
One possible plot could be that a powerful dark wizard, other than Voldemort, steals baby Harry for his own dark purposes. Maybe he wants to raise Harry to be his apprentice in the dark arts. He could take Harry to a hidden lair far away from the wizarding world, and as Harry grows up, he starts to suspect that his 'guardian' is not a good person.
One possibility could be that a Slytherin student steals money from other students' vaults at Gringotts. They might use magic to bypass the security. For example, they could use an Imperio - like spell on a goblin guard. Then, the other characters, like Harry, Hermione and Ron, start to investigate when they notice their friends are missing money.
Maybe it could be about Harry Potter being reborn as a Cybertronian baby and having to adapt to the unique culture and abilities of the Cybertronians. He might discover he has some special powers related to both his wizarding past and his new Cybertronian form.
Well, perhaps in this fanfiction, Harry Potter stumbles upon a baby while on one of his adventures. Maybe the baby has some sort of magical power that he has to protect from the dark forces. It could also be that the baby is related to an old prophecy and Harry has to figure out how to keep it safe and fulfill the prophecy at the same time.
A powerful foreign dark wizard could be the main villain. He might have heard of the prophecy about Harry Potter and decided to steal him from the Dursleys. This wizard could come from a far - off land with different and more dangerous dark magic, and his motives could be to gain ultimate power in both his own land and the British wizarding world by controlling Harry.
In this fanfiction, it could be that a magical accident occurs during a potion - making class. Harry accidentally drinks a wrong potion which transforms him into a baby. Dumbledore then decides to keep Harry at Hogwarts, with the teachers taking turns to look after him. Meanwhile, Neville could be the one who discovers a clue about how to reverse the transformation by observing some strange behavior of magical plants in the school's greenhouse.
In this fanfiction, perhaps Harry's hollow state gives him some unique powers that are different from his normal wizard abilities. For example, he could have enhanced speed or the ability to disappear in a different way. And Voldemort might sense this strange new power and be both intrigued and threatened by it.
One possible plot could be that the baby sister has some unique magical abilities from the start. Maybe she can communicate with magical creatures in a way that no one else can. This could lead to all sorts of adventures where Harry and his friends have to protect her from those who might want to use her abilities for evil. For example, Voldemort's remaining followers might see her as a new threat or a tool to be used.
A possible plot could be that a baby dragon is found by a group of first - year students. They initially think it's just a strange lizard - like creature. But as it grows and starts to show dragon - like features, they realize what it is. They then try to find a way to get it back to its natural habitat, which might be in Romania where Charlie Weasley works with dragons. Along the way, they learn a lot about different types of dragons and the importance of protecting magical creatures.
Well, one possibility could be that a dark wizard other than Voldemort kidnaps Harry. Maybe this wizard wants to use Harry's magic for his own evil purposes. He could take Harry to a hidden lair and try to train him to be evil from a young age. However, the wizarding world soon realizes Harry is missing and Dumbledore leads a search party to rescue him.
In this fanfiction, perhaps it starts with a strange prophecy related to Harry becoming a hollow as a baby. The wizarding world might be in chaos because they don't understand what this means for the future. As a baby - hollow, Harry could have some special powers or abilities that are unknown to normal wizards. His friends at Hogwarts later on might discover his true form gradually and help him to either reverse it or use it to fight against a new, greater evil in the wizarding world.