What kind of magic would Harry Potter use to make an island in fanfiction?

He would probably use magic for more practical and lethal purposes. For example, the Imperio curse could be used to control his targets, making it easier for him to complete his assassinations. The Disillusionment Charm would be crucial for him to blend into the shadows and get close to his victims unnoticed. And he might also use the Stunning Spell not just to incapacitate, but perhaps as a precursor to a more deadly attack.

A natural healer in the Harry Potter world might use Herbology - based magic. They could use plants like dittany which is known for its healing properties on wounds. By chanting simple spells over the plant extracts, they could enhance their healing powers. For example, a spell to accelerate the dittany's ability to close a wound quickly.

He might use the Patronus charm. The Patronus is not just for fighting Dementors. In this fanfiction, it could be that the positive energy of the Patronus is used to heal Tony Stark's soul. Maybe Stark has some sort of emotional or mental trauma from his battles, and the Patronus charm can soothe and heal those wounds.

Perhaps he uses the island as a secret training ground. He could practice advanced spells away from the prying eyes of Hogwarts faculty and students. Harry might also build his own magical fortress on the island for protection and privacy.

If Harry is raised by Sesshomaru, the magic he learns would be a blend of wizarding magic and something more influenced by Sesshomaru's world. He could learn to use his magic in a more silent and stealthy way, as Sesshomaru is often a silent predator. His magic might also be more attuned to nature, as Sesshomaru has a connection to the natural world in his own realm. Harry might be taught to use magic to create illusions not just for fun but as a serious combat tactic, and he could learn to manipulate his magic in ways that are more fluid and less structured than traditional wizarding magic, allowing for more creative and unexpected attacks.

They could use ice - making magic to create ice bridges to cross otherwise uncrossable gaps, like the chasms in the mountains around Hogwarts. For example, when the characters are on a quest to find a rare magical herb on a cliff - side, the ice - making wizard among them could freeze the waterfall next to it to form a staircase of ice leading up to the herb.

Another possibility is that he uses some ancient magic that he discovers in the Forbidden Forest or some old wizarding books. This magic could be more in tune with nature and be used specifically for growing food. It might involve some sort of connection with the earth and the natural cycles of growth.

He might introduce more fair lending practices. In the wizarding world, some families or individuals might have been unfairly treated when it comes to borrowing money from the bank. Harry could change that.

He would probably learn basic but very powerful defensive magic first. Merlin would know the importance of protecting oneself, so things like a strong Shield Charm or basic protective enchantments would be among the first things Harry learns.

Perhaps it's an island with a hidden wizarding school, similar to Hogwarts but with its own distinct features. There might be ancient spells protecting the island, and the architecture could be a blend of different magical styles. Harry could have discovered this island during one of his adventures and decided to make it his own. He might use it as a sanctuary for those in need or as a place to study and preserve rare magic.