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.
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.
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.
Perhaps Harry sees a bit of himself in Atreus. Atreus is on a journey of self - discovery and growth, much like Harry was during his years at Hogwarts. Harry could be drawn to Atreus' courage and determination, and so he decides to save him when he's in trouble. It could also be that Harry is just exploring this new and strange world of God of War and when he comes across Atreus, he feels compelled to protect him as he would any other innocent in his own world.
In some fanfictions, Harry might use his magic skills. For example, he could use spells to protect Naruto from a powerful enemy. Maybe he casts a shield charm to block an attack that Naruto couldn't avoid on his own.
Yes, there might be. The 'Harry Potter' and 'One Piece' (where Marineford is from) fanfic communities are quite large and creative. There could be a crossover where Harry Potter somehow saves Ace at Marineford. You can check fanfic platforms like Archive of Our Own or FanFiction.net to see if such a story exists.
It could be some dark wizards who want to use the centaur's parts for potions. They might be following some ancient, dark magic recipe that requires centaur hair or hooves. So they hunt down the centaur, but Harry gets in their way.
In this fanfiction, perhaps the centaur is in a situation where it's about to be sacrificed in some dark ritual. Harry discovers this and races against time to stop it. He calls upon his friends Hermione and Ron for help. Hermione uses her vast knowledge of magic to figure out how to break the dark magic circle, while Ron provides some much - needed comic relief during the tense situation. Harry, of course, is the one who ultimately uses his powerful Patronus charm to dispel the dark forces and save the centaur.
Zoe could be a new student at Hogwarts who gets into trouble. Maybe she's a first - year who wandered into the Forbidden Forest by accident and Harry has to save her from the dangerous creatures there.