There's a chance that he'll meet some sort of magical creature that has made the cupboard its home. This could be a friendly creature that helps him get out or a more mischievous one that makes his situation even more difficult. He'll have to use his wits and magic skills to deal with it.
He might have to face challenges that are different from those in the wizarding world. For example, the rules of the game could be strange and he'd need to figure them out quickly. Maybe he'd encounter characters from other fictional universes or versions of his friends with altered personalities.
He could find himself in a really tough situation. For example, if he's in the middle of a feud between two magical factions in the fanfiction. He would have to use his wits and skills to try and find a way out or a solution that satisfies both sides. He might also start to question his own beliefs and loyalties as a result of being in this middle position.
In this fanfiction, Harry might use the staff for various magical purposes. Maybe it could enhance his existing powers. For example, it could help him perform more complex spells with greater ease. He could also use it to defend himself in a more unique way compared to just using his wand.
Well, perhaps Harry's new haircut makes him look completely different and his friends don't recognize him at first. It could be a humorous situation where they keep asking who he is until he reveals himself.
In this fanfiction, Harry might use the phoenix for various magical tasks. The phoenix could help him in his battles against Voldemort. For example, it could carry messages quickly or even heal his wounds with its tears.
In the 'Harry Potter gets knighted' fanfiction, perhaps Harry is honored for his heroic deeds against Voldemort. He might be knighted in a grand ceremony at Hogwarts, with all his friends and professors present. The Ministry of Magic could finally recognize his great contributions to the wizarding world.
Well, they might start using their magic in ways that are unique to the Harry Potter world. Maybe they'll try to use wands instead of their usual powers. They could also interact with the Harry Potter characters in strange ways, like teaching Hermione some of their own spells or getting into a magical duel with Snape.
In the 'Harry Potter gets a second wand fanfiction', it could change his relationships too. His friends might be both amazed and a bit worried. Hermione would probably be eager to study the implications of having two wands. Ron might be a bit jealous at first. And Harry himself would need to learn how to balance the power of two wands, which could be a real struggle, both physically and mentally, as different wands have different 'personalities' and he'd have to master them both.
Perhaps in this fanfiction, the custom wand is created by a very eccentric wand - maker. This wand - maker could have some strange ideas and methods. The wand could be designed to work in harmony with Harry's emotions. So when he's feeling angry, it might produce a more powerful spell, and when he's calm, it could be more precise. This would add a new dimension to Harry's magical abilities and how he uses them in different situations.
Well, perhaps Harry discovers some special power within the Potter ring. It could be a source of great magic that he uses to protect Fleur in dangerous situations. Maybe the ring has a connection to his family's past and gives him insights into secrets long forgotten.