Ron might be there too. He could use his skills in handling magical creatures to populate the island with friendly ones. And he could also help with fishing in the surrounding waters using magic, providing food for those on the island.
Perhaps Hagrid could assist. He has a deep understanding of magical creatures and could help Harry populate the island with them. He might also use his strength to help with the physical construction, like moving large rocks or trees.
Dumbledore, if he were still alive in the fanfiction, could offer his wisdom. He might guide Harry on the moral and magical implications of creating an island. He could also provide some powerful spells or artifacts that would aid in the construction process.
One challenge would be the goblins. They are very protective of Gringotts and would not easily give up control. They have their own laws and traditions regarding ownership. Harry would have to deal with their resistance and find a way to convince them or negotiate with them.
His friends from Hogwarts, like Ron and Hermione, are likely to help. Ron could bring his family's practical knowledge of wizarding homes and Hermione would contribute with her extensive research skills.
Obviously, Hermione and Ron would be great supporting characters. Hermione could help Harry with all the legal and magical aspects of buying the island, like researching any magical properties or laws related to island ownership. Ron could be there for the more practical and fun parts, like fishing (with magic - of course) and exploring the island.
Hermione would be a great help. Her vast knowledge of magic and books could provide the necessary information for building the planet, like the right spells and magical theories.
Dumbledore might also play a role. He has vast knowledge and experience. He could offer some wise advice or even provide a special magical item or spell that is crucial for the unicorn's healing.
Dumbledore might offer some guidance. He has vast knowledge and experience. He could tell Harry about the significance of different elements in a staff and how to combine them to make a truly powerful and unique magical tool.
Dumbledore might help in a spiritual or advisory way. Even though he's passed away, his wisdom could be passed on through memories or some magical means. Also, Hagrid could be a great help. He could assist in building areas suitable for magical creatures with his love and understanding of them.
His best friends Hermione and Ron would surely be there to help. Hermione with her vast knowledge of magic could research about the egg, and Ron with his loyalty would stand by Harry's side in any danger related to the egg.