In such a fanfiction, it could be that Atreus has somehow ended up in Hogwarts. There could be a conflict between the students who are suspicious of this new arrival and Harry has to step in to protect Atreus. Harry would likely use his knowledge of the magical world and his courage to ensure Atreus's safety. He might also introduce Atreus to the wonders of magic, like flying on a broomstick or using potions to heal wounds.
Another possibility is that Atreus is in his own world facing a threat that only Harry's magic can counter. For example, a dark force in the God of War universe that is immune to Atreus's normal attacks. Harry, with his ability to think on his feet and his vast array of spells, could arrive just in time. He would need to adapt to the new environment quickly, perhaps learning about Atreus's powers and how they can work together to defeat the common enemy. This would create an interesting dynamic between the two characters, with their different backgrounds and abilities coming together for a common goal.
I'm sorry, I haven't read a specific 'harry potter saves atreus fanfiction' myself, but you can try searching on popular fanfiction websites like Fanfiction.net or Archive of Our Own. There might be some interesting stories there.
The obvious antagonists would be the Death Eaters. They are Voldemort's followers and are often causing trouble in the wizarding world. In this fanfiction, they might be the ones who have put Cedric in danger, either to lure Harry or for some other dark purpose.
In this fanfiction scenario, Harry Potter might use his magic to heal Atreus if he gets injured. He could brew potions using the ingredients available in the God of War world, if possible. Harry could also teach Atreus some basic magic, like how to levitate objects. This would give Atreus an edge in combat. And when they are facing a really powerful enemy, Harry could use powerful spells like the Cruciatus Curse (although it's an Unforgivable Curse, but in a life - or - death situation in a different world, who knows) to defeat the enemy and save Atreus.
Dark wizards or witches who are on a power - hungry spree could be the antagonists. They might see Daphne as an easy target or a way to get to Harry Potter himself. So they kidnap her to lure Harry into a trap.
The Death Eaters are a likely choice. They might target Susan Bones because of her family's connection to the wizarding world. For example, her aunt Amelia Bones was a well - known figure, and the Death Eaters could be after something related to her or the Bones family in general.
Well, it might involve a lot of things. First, Harry Potter as a werewolf would likely have to navigate the Twilight - style werewolf pack dynamics. He might have a new set of powers or limitations based on how werewolves are portrayed in Twilight. There could be a whole new set of relationships formed, perhaps with Twilight's vampires or other werewolves. And it would also likely include some sort of conflict or adventure that combines elements from both the Harry Potter and Twilight worlds, like fighting a dark wizard who also has some connection to the Twilight vampires or something.
It would probably involve a crossover of the two universes. Harry Potter might encounter Deidara's unique form of art which is explosive in nature. There could be battles where magic and explosive art are pitted against each other.
It might involve Harry having Wolverine - like abilities. Maybe he could have retractable claws made of magic instead of adamantium. He could use these claws in battles against Voldemort and his Death Eaters. Also, Harry could inherit Wolverine's healing factor, which would make him even more difficult to defeat. The story could also have Wolverine - type characters in the wizarding world, like a wizard with a similar tough - guy attitude and a penchant for fighting.
It might involve a lot of world - building around the relationship. Since Merope Gaunt is from an old and rather dark wizarding family, there could be elements of her family's influence on their relationship. And for Harry, his more modern - day values might clash with the traditional ways of the Gaunt family.
The Dursleys are the most likely abusers as in the original Harry Potter story, they were the ones who mistreated Harry. They could be the ones from whom Bellatrix saves Harry in the fanfic.