Finding a truly safe place is a huge challenge. Voldemort has a vast network of Death Eaters and spies. So, even if Harry thinks he has found a refuge, it could be discovered. Also, he may face internal struggles. The pressure of being hunted could make him doubt his own abilities and decisions. And he has to keep his friends safe too, which adds to the difficulty.
One challenge could be betrayal. There might be some so - called allies who are secretly working for Voldemort. Another is the lack of resources. If he is constantly on the run, he may not have access to enough food, water or magical supplies. And he has to be constantly vigilant against dark magic spells that Voldemort might send his way.
Well, in many fanfictions, Harry might use his knowledge of hidden places in the wizarding world like the Room of Requirement. He could also rely on the help of his friends. For example, Hermione might use her vast knowledge of spells to create a hiding place or a protective charm. And Ron could be there to offer physical protection if needed.
One challenge could be dealing with the traditionalist teachers and pure - blood families. They might resist any changes Harry tries to make as they are used to the old ways. For example, if Harry wants to introduce muggle - born friendly policies, some of the old - school pure - bloods might oppose it.
One challenge could be the basilisk's own will. Even if Harry has the ability to control it, the basilisk is a powerful and ancient creature with its own instincts. It might resist Harry's control from time to time, especially when it comes to situations that go against its natural behavior, like being made to not attack innocent students.
Perhaps Harry has a plan to outwit Voldemort in the long run. By seeking help, he can get closer to Voldemort, understand his weaknesses better, and then use that knowledge against him. It's a risky but potentially effective strategy, like a spy infiltrating the enemy's camp.
One challenge could be the unfamiliarity with the Fairy Tail world. Different rules of magic and different types of magical creatures might be new to Harry. Another is that the Fairy Tail characters themselves might be very powerful and have their own unique abilities that Harry has to figure out how to counter.
Harry could put himself in great physical danger. Voldemort might not be willing to help without exacting a high price, like Harry's own life or his magic. And even if Voldemort does seem to offer help, it could be a trap to harm Harry.
One challenge could be controlling the intensity. Lightning is a very powerful force, and it might be difficult for Harry to rein it in. He could accidentally cause too much destruction when he just wants to create a small spark.
The Dementors are a huge challenge. Their presence alone can drain his happiness and will to escape. He has to find a way to avoid them or protect himself from their effects.
The wizarding world might be in shock. People who have always seen Voldemort as the ultimate evil would be confused. They would have to re - evaluate their views on Voldemort. Harry, on the other hand, would be in a very strange situation. He might be distrusted by some of his friends who think he has made a deal with Voldemort.
One challenge could be controlling the assassin's violent tendencies. Since the person is being groomed to be an assassin, it's likely they have a natural inclination towards violence, and Harry has to find a way to temper that while also teaching self - defense.