One possible reason could be for speed. The Firebolt is known for its incredible speed in the Harry Potter series, and Harry might need it for faster travel between Hogwarts and other places, or for Quidditch matches to outrun his opponents more easily.
A possible back story could be that the Warforged was created as a tool for a powerful wizard. Over time, it absorbed magical knowledge from its master. After the wizard's untimely death, the Warforged, now free, decided to continue the study of magic on its own, using the knowledge it had gained. It wandered the land, seeking more magical secrets and ways to improve its skills.
Once in a DND 5E game on Reddit, a player's character, a clumsy wizard, tried to cast a simple spell to light a torch. But instead of the torch, he set his own robes on fire. It was hilarious as he ran around panicking while the other players just watched in shock and then burst out laughing.
Maybe he loves the idea of the Firebolt in the fanfiction. It could be that the stories expand on his experiences with the Firebolt in a really exciting way.
There was a story where a rogue player on Reddit was trying to steal from a powerful mage. He thought he was being so sneaky, but he accidentally stepped on a magical rune that made his shoes sing every time he took a step. It was really funny as he tried to run away from the mage while his shoes were singing 'La - la - la' loudly.
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.
There's a fanfic where Voldemort curses the Firebolt, and Harry has to remake it using ancient magic and rare materials. The process is full of challenges and discoveries.
In one of our adventures in Waterdeep for Dragon Heist, our group of adventurers got into a tavern brawl. The wizard accidentally cast a spell that made everyone's hair stand on end. We all looked like porcupines. It was so funny that even the angry tavern patrons couldn't help but laugh. And instead of fighting more, we all ended up having a drink together.
During a mission in Waterdeep for Dragon Heist, our cleric was supposed to heal a sick person. But instead, he misread the spell and made the person's nose grow really long, like Pinocchio. It caused chaos in the town square as everyone was trying to figure out what happened. We had to run away from the angry mob while still laughing at the cleric's mistake.
Harry is the main one, but other characters could be involved in different ways. Neville could accidentally stumble upon Harry's secret project and, in his clumsy but kind - hearted way, end up helping. Luna Lovegood might offer some out - of - the - box ideas with her unique perspective on magic. And Dumbledore, with his vast knowledge and wisdom, could be a guiding figure in the background, giving Harry some cryptic advice that helps him in the creation of the Firebolt.