His relationship with the teachers would also be different. Snape, for instance, might be more conflicted about Harry. On one hand, he's in Slytherin which Snape favors, but on the other hand, he's still Harry Potter. And Dumbledore would have to watch Harry from a different perspective, perhaps guiding him in a more subtle way to make sure he doesn't get too influenced by the darker aspects of Slytherin house.
His relationship with Ron would be very different. Ron might be initially distrustful or even hostile towards Harry in Slytherin. But as the story progresses, they could come to understand each other better. Harry's relationship with Hermione could also change. She might be more cautious around him at first, but then realize that Harry is still the same person deep down. And his relationship with Draco would be much more complex. They could start as rivals, but then become allies in some situations, as they both have a connection to Slytherin.
Their relationship with Ron would be strained at first. Ron has a pre - conceived notion about Slytherin, so he might be suspicious of Harry and Hermione. But as time goes on, he realizes that they are still the same friends and they work together to bridge the gap between Gryffindor and Slytherin.
His relationship with his enemies like Voldemort would also be affected. If Regina has some sort of power or influence over Harry, Voldemort might see him as an even greater threat or an easier target. Harry might also have different ways of defending himself, influenced by Regina's methods or the new environment he's in. For example, Regina might have her own way of dealing with dark magic that she teaches Harry, which changes how he approaches Voldemort and his Death Eaters.
His relationship with Hermione might become more strained. Hermione, being very rule - bound and having a strong sense of right and wrong, might be very wary of Harry's new connection to Morgana. Ron, on the other hand, might be more accepting at first, but then start to worry as Harry shows signs of changing. With Dumbledore, there could be a whole new level of secrecy and trust issues, as Dumbledore tries to guide Harry while also being cautious of his Morgana - influenced powers.
His relationship with Hermione would be very different. Hermione, who is an advocate for house - elf rights, would be in a strange position. She might try to help Harry break the spell, but also be conflicted about treating him like a normal house - elf. With Ron, Ron might not take Harry as seriously at first in his house - elf form, but then realize that it's still Harry and they need to work together. And with Snape, Snape would probably be even more dismissive of Harry as a house - elf, but Harry would still find ways to get under his skin.
His relationship with Ron and Hermione would be very different. Since he's been raised by the founders, he might be more aloof from the typical Gryffindor camaraderie. He could see Ron's insecurities in a different light, perhaps being less patient with them. And with Hermione, he might be more critical of her book - learning approach as he's been taught by the founders themselves.
He might start by promoting fairness and equality within Slytherin. In the original series, Slytherin is often associated with pure - blood supremacy. Harry, as head, could break that stereotype. He could encourage students from all backgrounds to work together and support one another, changing the cut - throat competition within the house to a more collaborative environment.
Harry's relationship with Snape would be complex. Snape, who already had a difficult relationship with Harry, might be even more hostile. He could see Harry's connection to the Grim Reaper as a sign of dark magic. But as the story progresses, Snape might come to realize that Harry is using his powers for good. And Harry, on the other hand, might start to understand Snape better, seeing that they both have a connection to a power that is often misunderstood. With the other students, some might be afraid of Harry and avoid him, while others might be drawn to his new - found power and mystery.
His relationship with Hermione and Ron would be strained at first. They would be confused and a bit scared. But as they see Harry resist the dark side, they would become more supportive. With Dumbledore, there might be a new level of secrecy and mistrust at the start, but Dumbledore would likely keep an eye on Harry to see how he develops. As for the other students, many would be afraid and avoid him, but some might be curious and try to befriend him to see what it's like to be around the heir of Voldemort.
If Harry's wand were to fuse with another, say Hermione's, it could create a stronger bond between them. They would have to rely on each other more to understand the new powers of the wand.