In this fanfiction, Draco would flaunt his family's signature spells. His magic would be more calculated and strategic, like setting up magical traps before the duel even starts. Harry's magical abilities would be more about his connection to his friends and the positive energy that gives him. He could use magic that is enhanced by his loyalty and friendship, like a spell that gets stronger the more he thinks about protecting those he cares about. During the duel, both of them would have to constantly adapt their magical abilities to counter each other's moves.
Well, perhaps Draco has some new-found knowledge or a secret weapon that gives him confidence to take on Harry for the Lord Black title. Harry, on the other hand, may be initially reluctant to engage in the duel but is pushed into it to protect the legacy of the Black family. During the duel, they both could discover things about the Black family history that changes their perspective on the whole matter.
If Harry is Salazar, he might have enhanced Parseltongue abilities. Salazar was known for his connection with snakes, so Harry could communicate with a wider variety of serpents and perhaps even gain more control over them. For Draco as Godric, he could have a stronger affinity for Gryffindor - like magic, such as a more powerful Patronus, perhaps in the form of a lion, representing Godric's courage.
Well, Harry has the unique ability to see Thestrals because he has witnessed death. It's possible that one of their children could inherit this ability too, depending on how the fanfiction plays out. Hermione is very good at time - turning spells, though it's a dangerous magic. Their kids might inherit an inclination towards time - related magic, but hopefully in a more controlled and legal way. And of course, both Harry and Hermione are good at defensive magic, so their children would surely inherit strong defensive magical abilities.
His magical abilities would likely be developed in a more archaic and powerful way. The founders had different areas of expertise, so Harry could inherit a wide range of skills. Maybe he'd be a master of defensive magic like Salazar Slytherin was known for some aspects of it, and also be proficient in charms like Helga Hufflepuff was with her kind magic.
In many fanfictions, when Draco finds out Harry is Lord Black, it often leads to a shift in their dynamic. It could make Draco more envious or it might force him to re - evaluate his views of Harry. For example, in some stories, Draco realizes that Harry has more power and influence in the wizarding world than he initially thought, which makes him both jealous and a bit intimidated.
In this fanfiction, their different magical abilities could be explored in a friendly competition. They could have a series of magical challenges where Harry uses his Gryffindor - like courage and quick thinking, and Viktor uses his Durmstrang training in elemental magic. Through this competition, they not only show off their abilities but also learn from and respect each other's skills.
Well, Morgana has a deep understanding of magic that is far more ancient than what is taught at Hogwarts. When she and Harry interact magically, her knowledge could enhance Harry's abilities. Maybe she could show him how to use magic without a wand, which is something she might be proficient in. In return, Harry's unique connection to the magic of love (as seen with his mother's protection) could have an impact on Morgana's magic. It could start to soften some of the darker aspects of her powers.
Harry's Patronus charm could be a very interesting element when it comes to interacting with Davy Jones. Since the Patronus is a positive and powerful form of magic, it could have an effect on the dark and cursed nature of Davy Jones and his crew. Maybe it could temporarily stun them or even start to break the curse on the crew. And Davy Jones' power over the kraken could be used against the wizarding world, but wizards could use their magic to either tame the kraken or create barriers to keep it at bay.
Maybe a mutual friend, like Hermione, could set up a situation where they have to work together on a project. As they work side by side, they start to understand each other better. Harry might realize that Draco isn't all bad, and Draco could see Harry's kindness and courage in a new light.
Harry's magic as the Master of Death is deeply rooted in the lore of the Deathly Hallows. His invisibility cloak, resurrection stone, and elder wand give him unique powers. Zatanna's magic, on the other hand, is more about incantations and spell - casting. Their abilities could interact in a way that Harry's use of the elder wand could enhance Zatanna's spells when she channels her magic through it. The resurrection stone might give her insights into the spirits of the dead which could help in her spell - work.