In this fanfic, a really cool plot could be that Harry has been secretly communicating with other wizards outside of his family through a magical object. They've been planning his escape for a long time. They send him a special charmed item, like a bracelet that can turn him invisible at will. He uses this to his advantage and slips away from his family during a chaotic moment, like when they're having a big argument. Then, he follows a series of clues left by his new friends to reach a safe haven, a hidden magical community where he can finally be free and learn more about his true potential.
One possible plotline could be Harry using magic in creative ways to evade the authorities as he escapes. For example, he might use a complex series of apparition spells combined with disillusionment charms.
One possible plotline could be that Harry discovers a hidden magical portal in Hogwarts that leads outside of Britain. Another could be that he fakes his own death and secretly boards a ship bound for a far - off magical land to escape the danger in Britain. Maybe he teams up with some international wizards who help him smuggle out of the country under the guise of a diplomatic mission.
One possible plotline could be Harry finding a hidden portal that leads to a parallel magical world where he can escape the troubles of his own wizarding world. He might encounter new magical creatures and spells there.
One possible plotline could be Harry discovering a hidden magical ability that helps him escape. For example, he might find out he can teleport short distances, which he uses to get away from the Dursleys' house when they are being particularly cruel. Another could be that he gets help from an unexpected magical creature that has been secretly observing him all along. Maybe a house - elf that takes pity on him and shows him a secret passage out of the house.
One possible plotline could be Harry discovering a long - lost family magic that gives him the power to communicate with magical creatures in a unique way. Another could be him using family magic to unlock hidden chambers in Hogwarts that were sealed by his ancestors. Or perhaps he uses it to protect his friends from a new and powerful dark wizard by tapping into ancient family spells.
Hermione would be a very likely character to help. She's smart and resourceful, and she would use her extensive knowledge of magic to come up with a plan for Harry's escape. Another could be Hagrid. He has a big heart and he's always been fond of Harry. He could provide a means of transportation, like his flying motorcycle or a secret passage he knows of. Also, Sirius Black might be involved. He's Harry's godfather and he would do anything to protect Harry from his family, so he could be a key figure in getting Harry out of that situation.
Hermione could be a likely helper. She's smart and resourceful, and she would likely believe Harry if he told her his reasons for escaping Dumbledore. She could use her vast knowledge of magic and spells to create distractions or to find ways to bypass Dumbledore's security measures.
Another plotline might involve Harry forming unique alliances with other druids. They could work together to protect an ancient druidic site from dark wizards who want to use its power for evil. This would lead to some exciting battles and magical duels.
Perhaps it focuses on his reasons for becoming a thief. It could be that he was forced into it by some difficult circumstances in his life. Like he was wrongly accused of something and had no way to prove his innocence, so he turned to stealing to survive and seek revenge.
In 'harry is a king fanfic', a possible plotline is Harry having to deal with a rebellion. He would need to use his wits and leadership skills to quell it. Also, his love life might be intertwined with his role as king, like falling in love with a princess from another land which could have political implications.