It could be Harry Potter himself, as he might be the one to explore the other planet. Hermione would also likely be there, using her vast knowledge to understand the new world. Ron might accompany them as well, providing his loyalty and humor.
Well, he could face a whole new set of challenges. Maybe the magic there works differently. For example, spells he uses on Earth might not have the same effect, or he could encounter a powerful dark force that he has to figure out how to defeat without the help of his usual Hogwarts friends and professors. He'd have to rely on his own wits and the skills he's learned over the years to survive and overcome difficulties.
One interesting idea could be how the magical world of Harry Potter would adapt to the different environment of another planet. For example, how would spells work in a planet with different gravitational forces or atmospheric conditions. Another idea might be the discovery of new magical creatures native to that other planet.
It could be a planet where magic is more powerful and less restricted. Harry, having faced so many limitations in the wizarding world he knew, would create a place where magic can be used freely for good. There could be no dark wizards or threats like Voldemort, and wizards could focus on exploring and expanding their magical abilities. For example, they could create new spells without the fear of them being used for evil.
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.
Harry may decide to have a more intuitive magic system. Instead of relying on wands, which can be lost or broken, the magical beings on his planet could use their minds and emotions to cast spells. The stronger the emotion or intention, the more powerful the spell. And to prevent misuse, there could be a natural balance in the planet's magic. If someone tries to use dark magic, the planet itself could resist and weaken the spell, teaching the user that dark magic is not welcome.
Well, perhaps it's a planet with its own system of magic. It might have a core made of pure magic essence which gives power to all the magic on the planet. And there could be different regions, like one area filled with floating islands where powerful wizards live.
Well, perhaps Harry uses his magic to shape the planet. He might create unique magical creatures and ecosystems. For example, he could make a forest where the trees are made of living fire that doesn't burn but gives warmth and light.
He would first need to understand the environment. If the planet has different gravity, he'd have to adjust his movements. For instance, if it has low gravity, he might accidentally float around until he gets used to it.
Perhaps he discovers the planet during one of his adventures. He could be using a new spell that accidentally transports him to this uncharted planet, and then through some series of events, he becomes the rightful owner. For example, he might save the planet from a great evil and as a reward, the planet's native beings make him the owner.